#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000000;
int main(){
  int N, M, K;
  cin >> N >> M >> K;
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> B[i];
  }
  vector<int> R(M);
  for (int i = 0; i < M; i++){
    cin >> R[i];
  }
  map<int, pair<vector<int>, vector<int>>> mp;
  for (int i = 0; i < N; i++){
    mp[B[i] % K].first.push_back(i);
  }
  for (int i = 0; i < M; i++){
    mp[R[i] % K].second.push_back(i);
  }
  int edge = 0;
  long long ans = 0;
  for (auto &P : mp){
    int r = P.first;
    vector<int> id1 = P.second.first;
    vector<int> id2 = P.second.second;
    int cnt1 = id1.size();
    int cnt2 = id2.size();
    edge += min(cnt1, cnt2);
    vector<int> B2, R2;
    for (int i = 0; i < cnt1;  i++){
      B2.push_back((B[id1[i]] - r) / K);
    }
    for (int i = 0; i < cnt2;  i++){
      R2.push_back((R[id2[i]] - r) / K);
    }
    sort(B2.begin(), B2.end());
    sort(R2.begin(), R2.end());
    if (cnt1 > cnt2){
      swap(cnt1, cnt2);
      swap(B2, R2);
    }
    assert((long long) cnt1 * cnt2 <= 100000000);
    vector<vector<long long>> dp(cnt1 + 1, vector<long long>(cnt2 + 1, INF));
    dp[0][0] = 0;
    for (int i = 0; i <= cnt1; i++){
      for (int j = 0; j <= cnt2; j++){
        if (j > 0){
          dp[i][j] = min(dp[i][j], dp[i][j - 1]);
          if (i > 0){
            dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + abs(B2[i - 1] - R2[j - 1]));
          }
        }
      }
    }
    ans += dp[cnt1][cnt2];
  }
  if (edge != min(N, M)){
    cout << -1 << endl;
  } else {
    cout << ans << endl;
  }
}