#include<stdio.h>
#include<string.h>
int main() {
    char bin[35];
    scanf("%s",bin);
    int len = strlen(bin);
    for(int i = 0; i < len; i++) {
        if(bin[i] != '0' && bin[i] != '1')
        {
            printf("Invalid Input");
            return 0;
        }
    }
    int signedvalue = 0;
    if(bin[0] == '0')
    {
        for(int i = 0; i < len; i++)
        {
        signedValue = signedValue*2 + (bin[i] - '0');
        }
    }
else
{
    int carry = 1;
    for(int i = len - 1;i >= 0; i--)
    {
        int bit = (bin[i] == '0') ? 1 : 0;
        bit += carry;
        carry = bit /2;
        bit = bit % 2;
        signedValue = signedValue + (bit << (len -1 - i));
    }
    signedValue = -signedValue;
}
printf("%d",signedValue);
return 0;
}