#include <iostream>
#include <cmath>
using namespace std;

int main() {
	string s;
	cin>>s;
	int b; cin>>b;
	int n = s.size();
	int sum = 0;
	for(int i = 0;i< n ;i++){
		if(s[i] == '1'){sum+=pow(b,n-i-1);}
		
	}
	cout<<sum;
}