#include<stdio.h>
#include<string.h>
int main()
{
    char b [33];
    int i,ndec = 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;
    }
}