import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


// 1-dimensional min cost matching (perfect for as)
long solve(const(long[]) as, const(long[]) bs) {
  debug {
    writeln("solve ", as, " ", bs);
  }
  const asLen = cast(int)(as.length);
  const bsLen = cast(int)(bs.length);
  assert(asLen <= bsLen);
  if (asLen == 0) {
    return 0;
  }
  alias Entry = Tuple!(long, "pos", int, "typ");
  auto es = new Entry[asLen + bsLen];
  foreach (i; 0 .. asLen) es[i] = Entry(as[i], 0);
  foreach (i; 0 .. bsLen) es[asLen + i] = Entry(bs[i], 1);
  es.sort;
  const inf = es[asLen + bsLen - 1].pos - es[0].pos + 1;
  long f0;
  // list of slopes, ls: as surplus
  long offL, offR;
  DList!long ls, rs;
  ls.insertBack(-inf);
  rs.insertBack(+inf);
  foreach (i; 0 .. asLen + bsLen) {
    if (es[i].typ == 0) {
      // shift to left
      const t = rs.front + offR;
      rs.removeFront;
      if (rs.empty) rs.insertFront(+inf - offR);
      f0 += t;
      ls.insertBack(t - offL);
    } else {
      // shift to right, chmin for 0->0
      const t = ls.back + offL;
      ls.removeBack;
      if (ls.empty) ls.insertBack(-inf - offL);
      f0 -= t;
      rs.insertFront(t - offR);
      const tt = rs.front + offR;
      if (tt < 0) {
        f0 += tt;
        ls.back += tt;
        rs.front = 0 - offR;
      }
    }
    debug {
      foreach (t; ls) write(t + offL, " ");
      write("; ", f0, "; ");
      foreach (t; rs) write(t + offR, " ");
      writeln;
    }
    if (i < asLen + bsLen - 1) {
      offL -= (es[i + 1].pos - es[i].pos);
      offR += (es[i + 1].pos - es[i].pos);
    }
    debug {
      foreach (t; ls) write(t + offL, " ");
      write("; ", f0, "; ");
      foreach (t; rs) write(t + offR, " ");
      writeln;
    }
  }
  return f0;
}

void main() {
  try {
    for (; ; ) {
      int M = readInt;
      int N = readInt;
      const K = readLong;
      auto A = new long[M]; foreach (i; 0 .. M) A[i] = readLong;
      auto B = new long[N]; foreach (i; 0 .. N) B[i] = readLong;
      A.sort;
      B.sort;
      if (M > N) {
        swap(M, N);
        swap(A, B);
      }
      
      long[][long] ass, bss;
      foreach (i; 0 .. M) ass[A[i] % K] ~= A[i] / K;
      foreach (i; 0 .. N) bss[B[i] % K] ~= B[i] / K;
      long ans;
      foreach (key, as; ass) {
        if (key !in bss) {
          ans = -1;
          break;
        }
        auto bs = bss[key];
        if (as.length > bs.length) {
          ans = -1;
          break;
        }
        ans += solve(as, bs);
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}