#include <bits/stdc++.h>
using namespace std;
int main() {
  int p = 0, n, mod;
  cin >> n >> mod;
  int sum = 0;
  for (int i = 0; i < n; i++) {
    int a, b;
    cin >> a >> b;
    sum += b - a + 1;
  }
  if (sum % mod == 0) {
    cout << "0";
    return 0;
  } else {
    while (sum % mod != 0) {
      sum++;
      p++;
    }
  }
  cout << p;
  return 0;
}
