#include<bits/stdc++.h>
using namespace std;

int main() {
    int T;
    cin >> T;
    while (T--) {
        long long N, K;
        cin >> N >> K;
        
        if (K >= N) {
            cout << (K - N) * 1 << endl;
        } else {
            cout << 0 << endl;
        }
    }
    return 0;
}