#include <iostream>
#include <cmath>
using namespace std;

int main() {
    int t;
    cin>>t;
    for(int j=0;j<t;j++) {
long long int x;
int b;
cin>>b>>x;
if (x==0) {cout<<"a"; return 0;}
x++;
unsigned long long int sum=0;
int counter=1;
while (sum<x) {
sum+=pow(b,counter)*counter;
counter++;
}
sum-=pow(b,counter-1)*(counter-1);
x-=sum;
int y=x%(counter-1);
if (y==0) y=counter-1;
x/=(counter-1);
x--;
int m = (int)(x/pow(b,counter-1-y))%b;
char n=m+97;
cout<<n<<endl;
}
}