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