using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static System.Math;
using System.Text;
using System.Threading;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Library;

namespace Program
{
    public static class ProblemF
    {
        static bool SAIKI = false;
        static public int numberOfRandomCases = 0;
        static public void MakeTestCase(List<string> _input, List<string> _output, ref Func<string[], bool> _outputChecker)
        {
        }
        static public void Solve()
        {
            var N = NN;
            var M = NN;
            var K = NN;
            var BList = NNList(N);
            var RList = NNList(M);
            var modKB = new LIB_Dict<long, List<long>>(_ => new List<long>());
            var modKR = new LIB_Dict<long, List<long>>(_ => new List<long>());
            foreach (var item in BList)
            {
                modKB[item % K].Add(item / K);
            }
            foreach (var item in RList)
            {
                modKR[item % K].Add(item / K);
            }
            var count = 0L;
            foreach (var item in modKB)
            {
                count += Min(modKR[item.Key].Count, item.Value.Count);
            }
            if (count < Min(N, M))
            {
                Console.WriteLine(-1);
                return;
            }
            if (N > M)
            {
                var t = modKR; modKR = modKB; modKB = t;
            }
            var ans = 0L;

            foreach (var item in modKB)
            {
                var bList = item.Value.OrderBy(e => e).ToArray();
                var rList = modKR[item.Key].OrderBy(e => e).ToArray();
                var saiteki = new long[bList.Length];
                for (var i = 0; i < saiteki.Length; ++i)
                {
                    var ret2 = LIB_Common.SanbunTansaku(0, rList.Length, mid =>
                    {
                        return Abs(bList[i] - rList[mid]);
                    });
                    saiteki[i] = ret2.k;
                }
                var dic = new Dictionary<(long, long, long, long), long>();
                Func<long, long, long, long, long> fun = null;
                fun = (bl, br, rl, rr) =>
                {
                    var key = (bl, br, rl, rr);
                    if (dic.ContainsKey(key)) return dic[key];
                    var ret = LIB_Common.SanbunTansaku(bl, br, mid =>
                    {
                        var leftCount = mid - bl;
                        var rightCount = br - mid - 1;
                        var rMoveLeft = rl + leftCount;
                        var rMoveRight = rr - rightCount - 1;
                        var rmid = Min(rMoveRight, Max(rMoveLeft, saiteki[mid]));
                        var ret2 = Abs(bList[mid] - rList[rmid]);
                        if (leftCount > 0)
                        {
                            ret2 += fun(bl, mid, rl, rmid);
                        }
                        if (rightCount > 0)
                        {
                            ret2 += fun(mid + 1, br, rmid + 1, rr);
                        }
                        return ret2;
                    });
                    return dic[key] = ret.val;
                };
                ans += fun(0, bList.Length, 0, rList.Length);
            }

            Console.WriteLine(ans);
        }
        class Printer : StreamWriter
        {
            public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
            public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { base.AutoFlush = false; }
            public Printer(Stream stream, Encoding encoding) : base(stream, encoding) { base.AutoFlush = false; }
        }
        static LIB_FastIO fastio = new LIB_FastIODebug();
        static public void Main(string[] args) { if (args.Length == 0) { fastio = new LIB_FastIO(); Console.SetOut(new Printer(Console.OpenStandardOutput())); } if (SAIKI) { var t = new Thread(Solve, 134217728); t.Start(); t.Join(); } else Solve(); Console.Out.Flush(); }
        static long NN => fastio.Long();
        static double ND => fastio.Double();
        static string NS => fastio.Scan();
        static long[] NNList(long N) => Repeat(0, N).Select(_ => NN).ToArray();
        static double[] NDList(long N) => Repeat(0, N).Select(_ => ND).ToArray();
        static string[] NSList(long N) => Repeat(0, N).Select(_ => NS).ToArray();
        static long Count<T>(this IEnumerable<T> x, Func<T, bool> pred) => Enumerable.Count(x, pred);
        static IEnumerable<T> Repeat<T>(T v, long n) => Enumerable.Repeat<T>(v, (int)n);
        static IEnumerable<int> Range(long s, long c) => Enumerable.Range((int)s, (int)c);
        static IOrderedEnumerable<T> OrderByRand<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x, _ => xorshift);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderBy<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderBy(x.OrderByRand(), selector);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x) => Enumerable.OrderByDescending(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderByDescending<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderByDescending(x.OrderByRand(), selector);
        static IOrderedEnumerable<string> OrderBy(this IEnumerable<string> x) => x.OrderByRand().OrderBy(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderBy(selector, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<string> OrderByDescending(this IEnumerable<string> x) => x.OrderByRand().OrderByDescending(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderByDescending(selector, StringComparer.OrdinalIgnoreCase);
        static string Join<T>(this IEnumerable<T> x, string separator = "") => string.Join(separator, x);
        static uint xorshift { get { _xsi.MoveNext(); return _xsi.Current; } }
        static IEnumerator<uint> _xsi = _xsc();
        static IEnumerator<uint> _xsc() { uint x = 123456789, y = 362436069, z = 521288629, w = (uint)(DateTime.Now.Ticks & 0xffffffff); while (true) { var t = x ^ (x << 11); x = y; y = z; z = w; w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)); yield return w; } }
        static bool Chmax<T>(this ref T lhs, T rhs) where T : struct, IComparable<T> { if (lhs.CompareTo(rhs) < 0) { lhs = rhs; return true; } return false; }
        static bool Chmin<T>(this ref T lhs, T rhs) where T : struct, IComparable<T> { if (lhs.CompareTo(rhs) > 0) { lhs = rhs; return true; } return false; }
        static void Fill<T>(this T[] array, T value) => array.AsSpan().Fill(value);
        static void Fill<T>(this T[,] array, T value) => MemoryMarshal.CreateSpan(ref array[0, 0], array.Length).Fill(value);
        static void Fill<T>(this T[,,] array, T value) => MemoryMarshal.CreateSpan(ref array[0, 0, 0], array.Length).Fill(value);
        static void Fill<T>(this T[,,,] array, T value) => MemoryMarshal.CreateSpan(ref array[0, 0, 0, 0], array.Length).Fill(value);
    }
}
namespace Library {
    class LIB_Dict<K, V> : Dictionary<K, V>
    {
        Func<K, V> d;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Dict(Func<K, V> _d) { d = _d; }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Dict() : this(_ => default(V)) { }
        new public V this[K i]
        {
            get
            {
                return TryGetValue(i, out var v) ? v : base[i] = d(i);
            }
            set
            {
                base[i] = value;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override int GetHashCode()
        {
            unchecked
            {
                var ret = 23;
                for (var e = GetEnumerator(); e.MoveNext();) ret = (ret * 37) ^ (e.Current.Key.GetHashCode() << 5 + e.Current.Key.GetHashCode()) ^ e.Current.Value.GetHashCode();
                return ret;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override bool Equals(object obj)
        {
            var o = (LIB_Dict<K, V>)obj;
            foreach (var kv in o)
            {
                if (!ContainsKey(kv.Key) || !this[kv.Key].Equals(kv.Value))
                    return false;
            }
            return o.Count == Count;
        }
    }
    class LIB_Deque<T>
    {
        T[] array;
        int front, cap;
        public int Count;
        public T this[long i]
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return array[GetIndex((int)i)]; }
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            set { array[GetIndex((int)i)] = value; }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Deque(long cap = 16)
        {
            array = new T[this.cap = (int)cap];
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        int GetIndex(int i)
        {
            if (i >= cap) throw new Exception();
            var r = front + i;
            return r >= cap ? r - cap : r;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void PushFront(T x)
        {
            if (Count == cap) Extend();
            if (--front < 0) front += array.Length;
            array[front] = x;
            ++Count;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public T PopFront()
        {
            if (Count-- == 0) throw new Exception();
            var r = array[front++];
            if (front >= cap) front -= cap;
            return r;
        }
        public T Front => array[front];
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void PushBack(T x)
        {
            if (Count == cap) Extend();
            var i = front + Count++;
            array[i >= cap ? i - cap : i] = x;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public T PopBack()
        {
            if (Count == 0) throw new Exception();
            return array[GetIndex(--Count)];
        }
        public T Back => array[GetIndex(Count - 1)];
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        void Extend()
        {
            T[] nb = new T[cap << 1];
            if (front > cap - Count)
            {
                var l = array.Length - front; Array.Copy(array, front, nb, 0, l);
                Array.Copy(array, 0, nb, l, Count - l);
            }
            else Array.Copy(array, front, nb, 0, Count);
            array = nb; front = 0; cap <<= 1;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Insert(long i, T x)
        {
            if (i > Count) throw new Exception();
            this.PushFront(x);
            for (int j = 0; j < i; j++) this[j] = this[j + 1];
            this[i] = x;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public T RemoveAt(long i)
        {
            if (i < 0 || i >= Count) throw new Exception();
            var r = this[i];
            for (var j = i; j > 0; j--) this[j] = this[j - 1];
            this.PopFront();
            return r;
        }
    }
    class LIB_Common
    {
        public struct RunLengthResult<T>
        {
            public long count;
            public T value;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public List<RunLengthResult<T>> RunLength<T>(IEnumerable<T> l)
        {
            T before = default(T);
            var cnt = 0;
            var ret = new List<RunLengthResult<T>>();
            foreach (var item in l)
            {
                if (!before.Equals(item))
                {
                    if (cnt != 0)
                    {
                        ret.Add(new RunLengthResult<T> { count = cnt, value = before });
                        cnt = 0;
                    }
                }
                before = item;
                ++cnt;
            }
            if (cnt != 0) ret.Add(new RunLengthResult<T> { count = cnt, value = before });
            return ret;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public List<T> LCS<T>(T[] s, T[] t) where T : IEquatable<T>
        {
            int sl = s.Length, tl = t.Length;
            var dp = new int[sl + 1, tl + 1];
            for (var i = 0; i < sl; i++)
            {
                for (var j = 0; j < tl; j++)
                {
                    dp[i + 1, j + 1] = s[i].Equals(t[j]) ? dp[i, j] + 1 : Max(dp[i + 1, j], dp[i, j + 1]);
                }
            }
            {
                var r = new List<T>();
                int i = sl, j = tl;
                while (i > 0 && j > 0)
                {
                    if (s[--i].Equals(t[--j])) r.Add(s[i]);
                    else if (dp[i, j + 1] > dp[i + 1, j]) ++j;
                    else ++i;
                }
                r.Reverse();
                return r;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public (int[] result, List<T> dp) LIS<T>(IEnumerable<T> array, bool strict) where T : IComparable<T>
        {
            var l = new List<T>();
            var ret = new List<int>();
            foreach (var e in array)
            {
                var left = -1;
                var right = l.Count;
                while (right - left > 1)
                {
                    var mid = (right + left) / 2;
                    if (l[mid].CompareTo(e) < 0 || !strict && l[mid].CompareTo(e) == 0) left = mid;
                    else right = mid;
                }
                if (right == l.Count) l.Add(e);
                else l[right] = e;
                ret.Add(l.Count);
            }
            return (ret.ToArray(), l);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public (long k, T val) SanbunTansaku<T>(long left, long right, Func<long, T> fun) where T : IComparable<T>
        {
            var size = right - left;
            var fib = new LIB_Deque<long>();
            fib.PushBack(1);
            fib.PushBack(1);
            while (fib[fib.Count - 1] * 2 + fib[fib.Count - 2] <= size)
            {
                fib.PushBack(fib[fib.Count - 1] + fib[fib.Count - 2]);
            }
            var valueLeft = left;
            var valueRight = right;
            Func<long, (bool isMax, T value)> calc = x =>
            {
                if (x < valueLeft || valueRight <= x) return (true, default(T));
                return (false, fun(x));
            };
            --left;
            var lv = calc(left);
            var m1 = left + fib.PopBack();
            var m2 = m1 + fib.Back;
            var m1v = calc(m1);
            var m2v = calc(m2);
            var rv = calc(right = m1 - left + m1 + fib.Back);
            while (fib.Count > 2)
            {
                if (m1v.CompareTo(m2v) < 0)
                {
                    rv = m2v; right = m2;
                    m2v = m1v; m2 = m1;
                    m1v = calc(m1 = left + fib.PopBack());
                }
                else
                {
                    lv = m1v; left = m1;
                    m1v = m2v; m1 = m2;
                    m2v = calc(m2 = left + fib.PopBack() + fib.Back);
                }
            }
            var ans = calc(left);
            for (var i = left + 1; i < right; ++i)
            {
                var na = calc(i);
                if (ans.CompareTo(na) > 0)
                {
                    ans = na;
                    left = i;
                }
            }
            return (left, ans.value);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public (double k, T val) SanbunTansaku<T>(double left, double right, Func<double, T> fun) where T : IComparable<T>
        {
            const double PHI = 0.6180339887;
            var lv = fun(left);
            var rv = fun(right);
            var m2 = left + (right - left) * PHI;
            var m2v = fun(m2);
            var m1 = left + (m2 - left) * PHI;
            var m1v = fun(m1);
            for (var i = 0; i < 200; ++i)
            {
                if (m1v.CompareTo(m2v) < 0)
                {
                    rv = m2v; right = m2;
                    m2v = m1v; m2 = m1;
                    m1v = fun(m1 = left + (m2 - left) * PHI);
                }
                else
                {
                    lv = m1v; left = m1;
                    m1v = m2v; m1 = m2;
                    m2v = fun(m2 = m1 + (m1 - left) * PHI);
                }
            }
            return (m1, m1v);
        }
    }
    class LIB_FastIO
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_FastIO() { str = Console.OpenStandardInput(); }
        readonly Stream str;
        readonly byte[] buf = new byte[2048];
        int len, ptr;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        byte read()
        {
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 2048)) <= 0)
                {
                    return 0;
                }
            }
            return buf[ptr++];
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        char Char()
        {
            byte b = 0;
            do b = read();
            while (b < 33 || 126 < b);
            return (char)b;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public long Long()
        {
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != '-' && (b < '0' || '9' < b));
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = (ret << 3) + (ret << 1) + b - '0';
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public double Double() { return double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
    class LIB_FastIODebug : LIB_FastIO
    {
        Queue<string> param = new Queue<string>();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        string NextString() { if (param.Count == 0) foreach (var item in Console.ReadLine().Split(' ')) param.Enqueue(item); return param.Dequeue(); }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_FastIODebug() { }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override string Scan() => NextString();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override long Long() => long.Parse(NextString());
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override double Double() => double.Parse(NextString());
    }
}