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