# Recursive Factorial

Given a single positive integer

**n**

, your task is to create a recursive function to calculate the factorial of **n**

. The factorial of

**n**

, denoted as **n!**

, is the product of all positive integers less than or equal to **n**

. For example, the factorial of 5 is **5! = 5 x 4 x 3 x 2 x 1 = 120**

.The factorial of 0 is defined as 1, i.e.,

**0! = 1**

.The first and only line of the input contains a single integer

**n**

(1 ≤ n ≤ 20), which represents the number to calculate the factorial of.The output of the program should be a single line containing the factorial of

**n**

.Input | Output |

5 | 120 |

0 | 1 |

2 | 2 |

#### Constraints

Time limit: 2 seconds

Memory limit: 512 MB

Output limit: 1 MB