#include<iostream>

#include<cmath>

using namespace std;

int main()

{

string s;

cin >> s;

int n = 0;

for(int i = s.length() - 1; i >= 0; i--)

n += (s[i] - '0') * pow(2, s.length() - i - 1);

cout << n;

return 0;

}