#include<bits/stdc++.h>
using namespace std;
int main (){
    int x,s;
    cin>>x>>s;
    int sum=0;
    int cnt=0;
    if (x<=10) {
        while (s) {
    	    int x1=s%10;
    	    sum+=x1*pow(x,cnt);
    	    x1=0;
    	    s/=10;
    	    cnt++;
	    }
    } else {
    	while (s) {
    		int x1=s%10;
    		if (x1>='A'&&x1<='Z') {
    			x1=int(x1)-55;
			}
			sum+=x1*pow(x,cnt);
    	    x1=0;
    	    s/=10;
    	    cnt++;
		}
	}
	cout<<sum;
return 0;
}