/**
 *  Author: AhSaN (JUST-22)
 *  Created: 06-09-2024  07:44:28
**/
#include <bits/stdc++.h>

#pragma GCC optimize("Ofast")
using namespace std;

void Sol(int Cs) {
  long long n, k;
  cin >> n >> k;
  cout << max(0ll, k - n) << "\n";
  
}

signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int Tc = 1;
  cin >> Tc;
  for (int Cs = 1; Cs <= Tc; Cs++) {
    Sol(Cs);
  }
  return 0;
}