A_Divisibility_Problem.cpp

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

void solve() {
    int a, b;
    cin >> a >> b;
    if (a % b == 0) {
        cout << 0 << endl;
    } else {
        cout << b - (a % b) << endl;
    }
}

int main() {
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}