Write a function that tells if a natural *n* is perfect.

A natural number is called *perfect*
if it is equal to the sum of all its divisors except itself.
For instance, 28 is perfect, because 28=1+2+4+7+14.

**Interface**

C++ | bool is_perfect(int n); |

C | int is_perfect(int n); |

Java | public static boolean isPerfect(int n); |

Python | is_perfect(n) # returns bool |

is_perfect(n: int) -> bool |

**Precondition**

*n* is a natural number.

**Observation**
You only need to submit the required procedure;
your main program will be ignored.

Public test cases

**Input/Output**

is_perfect(28) → true

is_perfect(1) → false

is_perfect(100) → false

is_perfect(0) → false

is_perfect(1) → false

is_perfect(100) → false

is_perfect(0) → false

Information

- Author
- Jordi Petit
- Language
- English
- Translator
- Carlos Molina
- Original language
- Catalan
- Other languages
- Catalan
- Official solutions
- C C++ Java Python
- User solutions
- C C++ Java Python