#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;
}