Problem:
Score: 300 points

Problem Statement

Find the minimum prime number greater than or equal to X.

Notes

A prime number is an integer greater than 1 that cannot be evenly divided by any positive integer except 1 and itself.

For example, 2, 3, and 5 are prime numbers, while 4 and 6 are not.

Constraints

2 \le X \le 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X

Output

Print the minimum prime number greater than or equal to X.

Sample Input 1

20

Sample Output 1

23

The minimum prime number greater than or equal to 20 is 23.

Sample Input 2

2

Sample Output 2

2

X itself can be a prime number.

Sample Input 3

99992

Sample Output 3

100003

Solution in Python (3.4.3) (judge verdict: Accepted)

X = int(input())

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

i = 0
while True:
    X2 = X + i
    if is_prime(X2):
        break
    else:
        i = i + 1
    
print(X2)