#include <bits/stdc++.h> using namespace std; int main() { int x,ans=0; string s; cin>>x>>s; 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; }