#include <stdio.h>

int main() {
    char c;
    unsigned int dec = 0, i = 1;

    char bits[32];
    int bit_corrente = 0;
    while ((c = getchar()) != '\n') {
        bits[bit_corrente++] = c - '0';
    }

    int j;
    for (j = bit_corrente - 1;j >= 0; --j){
        if (bits[j] == 1){
            dec += i;
        }
        i *= 2;
    }

    printf("%d\n", dec);
    return 0;
}