include<bits/stdc++.h>

using namespace std; int main(){

int n;
char x[100];
long long res=0, base=1;
scanf("%d%s", &n, x);
int len = strlen(x);
for(int i=len-1;i>=0;i--){
    int num = x[i] - '0';
    res += num * base;
    base *= n;
}
printf("%lld", res);
return 0;

}