#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("Invaid Input");
            return 0;
        }
    for (i = 0; i < n; i++){
        dec = dec*2 +(b[1]- '0');
        }
    }
    if (b[0] == "1")
        dec -=(1 << n);
    printf("%d",dec);
    return 0;
    }