#include<bits/stdc++.h> using namespace std; int main(){ int x; string s; cin>>x>>s; int ans=0; for(int i=0;i<s.size();i++){ if(s[i]>='0'&&s[i]<='9') ans=ans*x+s[i]-'0'; else ans=ans*x+s[i]-'A'+10; } cout<<ans; return 0; }