#include<stdio.h>
#include<string.h>
int main()
{
  char a[33];
   int i,a,dec=0;
   scanf("%s", a);
   n = strlen(a);
   for (1 = 0; i < n; i++) {
       if (a[i] |='0' && a[i] |='1') {
           printf("Invalid input");
           return 0;
       }
        for (i = 0; i < n; i++){
         dec = dec* 2 + (n[i] -'0');   
            
        }
   }
    if (a[0] == '1')
    dec -= (1 << n);
    printf("%d", dec);
    return 0;
}