#include<iostream>
#include<string>
#include<stdio.h>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include <math.h> using namespace std;
int a;
char b[];
float s;
int main(){
scanf("%d %s",&a,b);
//printf("%s\n",b);
int len = strlen(b);
s= ;
for(int i = ; i < len ; i++)
{
int t = ;
if(b[i] >= 'A')
t = b[i] -'A' + ;
else
t = b[i] - ''; s += pow(a,-i+) * t;
}
s *= ;
s = floor(s + 0.5);
s /= ;
printf("%0.4f\n",s);
//printf("%s\n",a);
return ;
}