#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  long long K;
  int P;
  cin >> N >> K >> P;
  K--;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
    A[i] = (P - A[i]) % P;
  }
  sort(A.begin(), A.end());
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> B[i];
  }
  sort(B.begin(), B.end());
  int tv = 0, fv = P;
  while (fv - tv > 1){
    int mid = (tv + fv) / 2;
    long long cnt = 0;
    for (int i = 0; i < N; i++){
      if (A[i] + mid < P){
        cnt += lower_bound(B.begin(), B.end(), A[i] + mid) - lower_bound(B.begin(), B.end(), A[i]);
      } else {
        cnt += B.end() - lower_bound(B.begin(), B.end(), A[i]);
        cnt += lower_bound(B.begin(), B.end(), A[i] + mid - P) - B.begin();
      }
    }
    if (cnt <= K){
      tv = mid;
    } else {
      fv = mid;
    }
  }
  cout << tv << endl;
}