#include <stdio.h>

int main() {
    char number[1024];
    scanf("%1023s", number);
    int n = strlen(number);
    int novo = 0;
    for (int i = 0; i < n; i++) {
        novo += ((number[i] - '0') * (1 << (n - i - 1)));
    }

    printf("%d", novo);
}