#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int tot = 0;
  for (int i = 0; i < n; i++) {
    int a, b;
    cin >> a >> b;
    tot += (b - a) + 1;
  }
  if (tot % k == 0) {
    cout << 0 << endl;
  } else {
    int val = tot / k;
    val++;
    cout << (val * k) - tot << endl;
  }
  return 0;
}
