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