#include <stdio.h>
#include <string.h>
int main()
{
    char b[33];
    int i,n,dec = 0;
    scanf("%s", b);
    n = strnlen(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);
}