#include<bits/stdc++.h>
using namespace std;
int ans,jz=1,p;
string s;
int main()
{
    cin>>p>>s;
    for (int i=s.size()-1;i>=0;i--)
    {
        if (isdigit(s[i]))
            ans+=(s[i]-48)*jz;
        else
            ans+=(s[i]-'A'+10)*jz;
        jz*=p;
    }
    cout<<ans;
    return 0;
}