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: Time Limit Exceeded)

x=int(input())

sosuu = [2]
A = 100000
for L in range(3, A, 2): # 2 以外の素数は奇数なので
    for L2 in sosuu:
        if L % L2 == 0:
            break # 素数でないことがわかったらそれ以上ループする必要はない
    else: # break で抜けることがなかったら L は素数（Python 特有の制御構文）
        sosuu.append(L)
for i in sosuu:
    if x<=i:
        print(i)
        break