#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
#define print(v) for(auto &u:v) cout << u << " "
#define printp(v) for(auto e:v) cout<<e.first<<" "<<e.second<<endl;
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define pb push_back
#define pf push_front
#define printl(li) for(auto &u:li) cout << u;
 
void solve()
{ 
   int n, k; cin >> n >> k;
   cout << k-n << endl;


   




}
 
int main()
{   
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t = 1; cin >> t;
    while(t--)
    {
       solve();
    }
    return 0;
}