def info(s):
    """Return a dict describing the string s.

    Keys:
      "first"  — the character at index 0
      "sixth"  — the character at index 5
      "last"   — the character at index -1
      "length" — total number of characters

    info("MISSION-CONTROL-7") -> {"first": "M", "sixth": "O",
                                  "last": "7", "length": 17}
    """
    pass