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