Get the next prime number!

You will get a number`n` (>= 0) and your task is to find the next prime number. 

Make sure to optimize your code: there will numbers tested up to about `10^12`.

## Examples

```
5   =>  7
12  =>  13
```

Difficulty: introductory

Starter code:

def is_prime(n):
	

Solutions:
from itertools import count

def is_prime(n):
    if n < 2: return False
    if n == 2: return True
    if n % 2 == 0: return False
    for div in range(2, int(n ** 0.5) + 1):
        if n % div == 0:
            return False
    return True

def next_prime(n):
    for candidate in count(n + 1):
        if is_prime(candidate):
            return candidate

def is_prime(n):
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0:
            return False
    return n > 1


def next_prime(n):
    i = n + 1
    while not is_prime(i):
        i += 1
    return i


def is_prime(num):
    if num < 2:
        return False
    for i in range(2, int(num**0.5)+1):
        if num % i == 0:
            return False
    return True


def next_prime(n):
    n += 1
    while not is_prime(n):
        n += 1
    return n

def is_prime(n):
    if n in (2, 3, 5):
        return True
    elif n < 5:
        return False
    elif n%2:
        i = 3
        flag = True
        while i*i <= n:
            if n%i == 0:
                return False
            i += 2
        return True
    else:
        return False

def nextPrime(n):
    i = n+1
    while not is_prime(i):
        i+=1
    return i