#include<bits/stdc++.h>
#include<string.h>
using namespace std; 
int main() {
       int b[100];
       int x,i,ans,j=0,k=0;
       string s;
       cin>>x>>s;
       for(i=s.length();i>=0;i--)
       {
           if(s[i]>='0'&&s[i]<='9')
            b[k++]=(int)s[i]-48;
            if(s[i]>='A'&&s[i]<='Z')
            b[k++]=(int)s[i]-55;
       }
      long long  int sum;
       for(i=0;i<k;i++)
       {
           sum+=pow(x,i)*b[i];
       }
       cout<<sum;
      return 0;
}