infinity

#include<iostream>
#include<cmath>
using namespace std;
int main(){
    int t;
    cin>>t;
    for(int k=0;k<t;k++){
        long long a,b;
        cin>>a>>b;
        int j=1;
        while(b - (pow(a,j) * j) >= 0){
            b-=pow(a,j)*j;
            j++;
        }
        long long h = b / j;
        long long j1 = j;
        long long thesi;
        thesi = h;
        char s[j1];
        for(int i=0;i<j1;i++){
            s[i] = 'a';
        }
        b = b % j1;
        int x = j1 - b;
        x--;
        char c = 'a';
        x = thesi / pow(a,x);
        x = x % a;
        c+=x;
        cout<<c<<endl;
    }
    return 0;
}