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: Wrong Answer)

X=int(input())
testX=int(X**(1/2))+2
primeset={2}
for i in range(3,testX):
    num=0
    for p in primeset:
        if i%p != 0:
            pass
        else:
            num=1
            break
    if num==0:
        primeset.add(i)
num = 0 
while num == 0:
    num=1
    for p in primeset:
        if X%p != 0:
            pass
        else:
            X+=1
            num=0
            break
    if num == 1:
        print(X)