#include<bits/stdc++.h>

using namespace std;
#define ll long long
#define int ll
# define double long double
const int N = 2e5 + 2, MOD = 1e9 + 7;
#define deb(x) cout<<#x<<"="<<x<<endl;
#define F first
#define S second


void solve() {
    int n, k;
    cin >> n >> k;
    cout << max(0ll, k - n);


}

signed main() {
    ios_base::sync_with_stdio(false);
    cout.tie(NULL);
    cin.tie(NULL);
//#ifndef ONLINE_JUDGE
//    freopen("output.txt", "w", stdout);
//    freopen("input.txt", "r", stdin);
//#endif
    int tt = 1;
    cin >> tt;
    for (int i = 0; i < tt; i++) {
//        cout << "Case " << i + 1 << ": ";
        solve();
        cout << "\n";
    }
}