#include <bits/stdc++.h>

using namespace std;

int main() {
    const int N = 100;
    int a[N] = {0};
    char s[N];
    cin >> s;

    //字符串的长度
    int length = strlen(s);

    for (int i = 0; i < length; ++i) {
        a[i] = s[i] - '0';
    }
    int sum = 0;
    for (int i = 0; i < length; i++) {
        sum += a[i] * pow(2, length - i - 1);
    }
    cout << sum << endl;
    return 0;
}