#include <bits/stdc++.h>   using namespace std;   void solve() {     long long n, k;     cin >> n >> k;     string ans =   ;     for (long long i = 0; i < n; i++) {       ans.push_back( a );     }     for (long long i = n - 2; i >= 0; i--) {       if (k <= n - i - 1) {         ans[i] =  b ;         ans[n - k] =  b ;         break;       }       k -= (n - i - 1);     }     cout << ans << endl;   }   int main() {     int t;     cin >> t;     while (t--) {       solve();     }   }   