#include <stdio.h>
#include<string.h>
int main(){
    char bin[40];
    if (scanf("%39s", bin) != 1){
        printf ("Inalid Input");
        return 0;
    }
    int len =strlen(bin)
    for (int i = 0; i < len; i++){
        if (bin[i] ! ='0'&& bin[i] != '1'){
            printf("Invalid Input");
            return 0;
        }
    }
    if (bin[0] == '0'){
        long long value =0;
        for (int i = 0; i <len; i++){
            value =value * 2 + (bin[i]-'0');
        }
        printf("%lld",value);
        return 0;
    }
    long long unsigned _value = 0;
    for (int i = 0; i < len; i++){
        unsigned_value = unsigned_value * 2 + (bin[i] -'0');

    }
    long long pow2 = 1;
    for (int i = 0; i < len; i++){
        pow2 *= 2;
    }
    long long singned_value = (long long )(unsigned unsigned);
    printf("%lld",signed_value);
    return 0;
}