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 ProblemA
    {
        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;
                var rList = modKR[item.Key];

                var vList = bList.Select(e => new { isBlue = true, v = e }).Concat(rList.Select(e => new { isBlue = false, v = e })).OrderBy(e => e.v).ToArray();

                var len = vList.Length * 2 + 1;
                var center = len / 2;
                var left = center;
                var right = center + 1;
                var seg = new LIB_DualSegTree<long>(len, 0, (x, y) => x + y);
                foreach (var item2 in vList)
                {
                    if (item2.isBlue)
                    {
                        seg.Update(left, center, item2.v);
                        seg.Update(center, right, -item2.v);
                        --center;
                    }
                    else
                    {
                        seg.Update(center + 1, right, item2.v);
                        if (center + 1 < right) seg[center + 1] = Min(seg[center + 1], seg[center]);
                        else seg[center + 1] = seg[center];
                        seg.Update(left, center + 1, -item2.v);
                        ++center;
                    }
                    left.Chmin(center);
                    right.Chmax(center + 1);
                }
                ans += seg[center];
            }

            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_DualSegTree<T> where T : IEquatable<T>
    {
        int n, height;
        T ti;
        Func<T, T, T> f;
        T[] dat;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_DualSegTree(long _n, T _ti, Func<T, T, T> _f)
        {
            n = 1; height = 0;
            while (n < _n) { n <<= 1; ++height; }
            ti = _ti;
            f = _f;
            dat = Enumerable.Repeat(ti, n << 1).ToArray();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_DualSegTree(IEnumerable<T> l, T _ti, Func<T, T, T> _f) : this(l.Count(), _ti, _f)
        {
            var idx = 0;
            foreach (var item in l) dat[n + idx++] = item;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        void Eval(long i)
        {
            if (dat[i].Equals(ti)) return;
            dat[(i << 1) | 0] = f(dat[(i << 1) | 0], dat[i]);
            dat[(i << 1) | 1] = f(dat[(i << 1) | 1], dat[i]);
            dat[i] = ti;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        void Thrust(long i)
        {
            for (var j = height; j > 0; j--) Eval(i >> j);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        void Thrust(long l, long r)
        {
            if (l == r) { Thrust(l); return; }
            var xor = l ^ r;
            var i = height;
            for (; (xor >> i) != 0; --i) Eval(l >> i);
            for (; i != 0; --i) { Eval(l >> i); Eval(r >> i); }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Update(long l, long r, T v)
        {
            if (l == r) return;
            if (r < l) throw new Exception();
            Thrust(l += n, r += n - 1);
            for (long li = l, ri = r + 1; li < ri; li >>= 1, ri >>= 1)
            {
                if ((li & 1) == 1) { dat[li] = f(dat[li], v); ++li; }
                if ((ri & 1) == 1) { --ri; dat[ri] = f(dat[ri], v); }
            }
        }
        public class LazySegTreeOperator
        {
            T rangeOperator;
            public T value => rangeOperator;
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            static public LazySegTreeOperator operator *(LazySegTreeOperator lhs, T rhs)
            {
                lhs.rangeOperator = rhs;
                return lhs;
            }
        }
        public LazySegTreeOperator this[long l, long r]
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => new LazySegTreeOperator();
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            set => Update(l, r + 1, value.value);
        }
        public T this[long idx]
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { Thrust(idx += n); return dat[idx]; }
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            set { Thrust(idx += n); dat[idx] = value; }
        }
    }
    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_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());
    }
}