AC

#include<bits/stdc++.h>
using namespace std;
int x_to_ten(string s,int x){
	int sum = 0,wei = 1;
	for(int i = s.size()-1;i>=0;i--){
		int t;
		if(s[i]>='0'&&s[i]<='9') t = s[i]-'0';
		else t = s[i]-'A'+10;
		sum += t * wei;
		wei *= x; 
	}
	return sum;
}
int main(){
	int k;
    cin >>k;
    while(k--){
        int x;
        string s;
        cin >> x >> s;
        cout << x_to_ten(s,x)<<endl;
    }
	return 0;
}