#include<bits/stdc++.h>
using namespace std;

int main() 
{
    int n;
    cin>>n;
    
    for (int t = 0; t < n; t++) 
	{
        int k;
        string s;
        cin >> k >> s;
        int ans = 0;
        int i = 0;
        while (s[i]) 
		{  
            int d;
            if (s[i] <= '9')
			{
				d = s[i] - '0';
			}
            else
			{
				d = s[i] - 'A' + 10;
        	}
            ans = ans * k + d;
            i++;
        }
    	cout<<ans<<"\n";
    }
    return 0;
}

C++ :

#include <bits/stdc++.h>
using namespace std;
 
typedef long long LL;
LL convert(int p, string s) {
    LL ans=0;
    reverse(s.begin(),s.end());
    for(int i=0; i<s.size(); i++) {
        if(s[i]>='A') ans+=(s[i]-'A'+10)*pow(p,i);
        else ans+=(s[i]-'0')*pow(p,i);
    }
    return ans;
}
 
int main() {
    int T;
    cin>>T;
    while(T--) {
        int p;
        string s;
        cin>>p>>s;
        cout<<convert(p,s)<<endl;
    }
    return 0;
}
 
/*
in:
2
8 1362
16 3F0
out:
754
1008
*/