## gcd

### Instructions

Write a function that takes two `uint` representing two strictly positive integers and returns their greatest common divisor.
If any of the input numbers is 0, the function should return 0.

> [In mathematics, the greatest common divisor (GCD) of two or more integers, which are not all zero, is the largest positive integer that divides each of the integers.](https://en.wikipedia.org/wiki/Greatest_common_divisor)

### Expected function

```go
func Gcd(a, b uint) uint {

}
```

### Usage

Here is a possible program to test your function:

```go
package main

import (
	"fmt"
	"piscine"
)

func main() {
	fmt.Println(piscine.Gcd(42, 10))
	fmt.Println(piscine.Gcd(42, 12))
	fmt.Println(piscine.Gcd(14, 77))
	fmt.Println(piscine.Gcd(17, 3))
}
```

And its output :

```console
$ go run .
2
6
7
1
$
```