#include<bits/stdc++.h>
using namespace std;
#define ll long long
void solve(){
    ll n, k;
    cin >> n >> k;

    if(n >= k){
        cout << 0 << '\n';
        return;
    }
    ll ans = (k - n);
    cout << ans << '\n';
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t = 1;
    cin >> t;
    while(t--){
        solve();
    }
    return 0;
}