#include<stdio.h>
#include<string.h>
int main()
{
    char bin[33];
    scanf("%s",bin);
    int n = strlen(bin);
    for(int i=0; i<n; i++)
    {
        if(bin[i] != '0' && bin[i] != '1')
        {
            printf("Invalid Input");
            return 0;
        }
    }
    if(bin[0] == '0')
    {
        int value = 0;
        for(int i = 0;i<n;i++)
        {
            value = value*2 + (bin[i] -'0');
        }
        printf("%d",value);
    }
    else
    {
        unsigned int value = 0;
        for(int i = 0; i < n; i++);
        {
            value = value * 2 + (bin[i] - '0');
        }
        int signedvalue = value -(1 << n);
        printf("%d",signedvalue);
    }
    return 0;
}