#include<stdio.h>
#include<string.h>
int main()
{
    char b[33];
    int 1,n,dec = 0;
    scanf("%s", b);
    n = strlen(b);
    for (1 =0; 1 < 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;
    
}