#include<bits/stdc++.h>
using namespace std;
int main()
{
	int x,i,len,ans=0;
	string s;
	cin>>x>>s;
	len=s.length();
	cout<<"len:"<<len<<endl;
	for(i=len-1;i>=0;i--)
	{
		cout<<"i:"<<i<<" s[i]:"<<s[i];
		if(s[i]>='A'&&s[i]<='Z')
		{
			ans+=(s[i]-55)*pow(x,len-i-1);
			//cout<<" ("<<s[i]-55<<")*pow("<<x<<","<<len-i-1<<")="<<(s[i]-55)*pow(x,len-i-1);
		}
		else
		{
			ans+=(s[i]-48)*pow(x,len-i-1);
			//cout<<" "<<s[i]-48<<"*pow("<<x<<","<<len-i-1<<")="<<(s[i]-48)*pow(x,len-i-1);
		}
		cout<<endl<<endl;
	}
	cout<<ans;
	return 0;
}