#include <stdio.h>
#include <math.h>

//returns the length of a string
int getStringLen(char *str)
{
  int count = 0;

  while (*(str + count) != '.')
  {
    count++;
  }
  return count;
}

//calculates the minimun index by the string length
int getStartIndex(int len)
{
  int index = 0;
  for (int i = 0; i < len; i++)
  {
    index += pow(2, i);
  }

  return index;
}

//returns the index associated with the binary "ab" string taken as parameter
int enumerate(char *string)
{
  char *characters;
  char *index = string;
  int num = 0;
  int i = 1;
  int len = getStringLen(string);
  int start = getStartIndex(len);

  if (string == NULL)
    return num;

  while (*index != '.')
  {
    int increment = (*index == 'a') ? 0 : pow(2, len - i);
    num += increment;
    i++;
    index++;
  }

  return start + num;
}

int main()
{
  int index = enumerate("bbb.");
  printf("%d\n", index);
  return 0;
}