#include <bits/stdc++.h>
#define nl '\n'
#define ll long long int
#define all(v) v.begin(),v.end()
#define print(v) for(auto data : v) cout << data << " "; cout << nl
using namespace std;
void solve() 
{
    int n,k; cin >> n >> k;
    if(n >= k) cout << 0 << nl;
    else cout << k-n << nl;
}
int main()
{
    ios_base::sync_with_stdio(false); cin.tie(NULL);

    int t; cin >> t; 
    while (t--) solve();

    return 0;
}