#include<bits/stdc++.h> using namespace std; long long n,a,mc,len; string x; int main() { cin>>n>>x; len=x.size(); mc=1; for(int i=len-1;i>=0;i--) { if(x[i]>='A'&&x[i]<='Z') { a=a+(x[i]-55)mc; mc=n; } else { a=a+(x[i]-48)mc; mc=n; } } cout<<a;

}