#include <stdio.h>
#include <string.h>
#include <math.h>

int twosComplementToDecimal(char *bin) {
    int len = strlen(bin);
    int decimal = 0;


    for (int i = 0; i < len; i++) {
        decimal = decimal * 2 + (bin[i] - '0');
    }

    if (bin[0] == '1') {
        decimal -= (1 << len);
    }

    return decimal;
}

int main() {
    char bin[32];
    scanf("%s", bin);
    printf("%d\n", twosComplementToDecimal(binary));
    return 0;
}