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