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 PyPy3 (2.4.0) (judge verdict: Accepted)

x = int(input())

# 自然数m以下の素数を返す
def primes(n):
    is_prime = [True] * (n + 1)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, n + 1):
        for j in range(i * 2, n + 1, i):
            is_prime[j] = False
    return [i for i in range(n + 1) if is_prime[i]]

def prime_numbers_under(m):
    # 素数を保持するset
    primes = set()

    # 2以上m以下の素数を数え上げる
    n = 2
    while n <= m:
        # 自身より小さい全ての素数で割り切れなければ、素数とみなせる
        if all(n % i != 0 for i in primes):
            primes.add(n)
        n += 1

    return primes

# 自然数m以上の素数を返す
def prime_numbers_over(m):
    # 素数を保持するset
    # primes = set()
    global p

    if m in p:
        return m

    while True:
        # 自身より小さい全ての素数で割り切れなければ、素数とみなせる
        if all(m % i != 0 for i in p):
            return m
        m += 1

# p = prime_numbers_under(x)
p = primes(x)

print(prime_numbers_over(x))