#include<stdio.h>
#include<string.h>
int main()
{
    char bin[35];
    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 << 1) | (bin[i]-'0');
        }
        int signedValue=value - (1u << n);
        printf("%d", SignedValue);
    }
    return 0;
}