TIJIE

#include <bits/stdc++.h>
using namespace std;
int main()
{
    long long n,sum=0,k=0;
    string s;
    cin>>n>>s;
    for(int i=s.size()-1;i>=0;i--)
    {
        if(s[i]>='A' && s[i]<='Z') sum+=(s[i]-55)*pow(n,k);
        else sum+=(s[i]-'0')*pow(n,k);
        k+=1;
    }
    cout<<sum;
}