input: 
  def is_happy(s):
      """You are given a string s.
      Your task is to check if the string is happy or not.
      A string is happy if its length is at least 3 and every 3 consecutive letters are distinct
      For example:
      is_happy(a) => False
      is_happy(aa) => False
      is_happy(abcd) => True
      is_happy(aabb) => False
      is_happy(adb) => True
      is_happy(xyy) => False
      """
  
output:     if len(s) < 3:
          return False
      for i in range(len(s) - 2):
          if s[i] == s[i+1] or s[i] == s[i+2] or s[i+1] == s[i+2]:
              return False
      return True