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 (3.8.2) (judge verdict: Accepted)

import random
def is_prime(q,k=50):
    q = abs(q)
    if q == 2: return True
    if q < 2 or q&1 == 0: return False
    d = (q-1)>>1
    while d&1 == 0:
        d >>= 1
    for i in range(k):
        a = random.randint(1,q-1)
        t = d
        y = pow(a,t,q)
        while t != q-1 and y != 1 and y != q-1: 
            y = pow(y,2,q)
            t <<= 1
        if y != q-1 and t&1 == 0:
            return False
    return True
X = int(input())
for i in range(X, 100004):
    if is_prime(i):
        print(i)
        break