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)

def getIsPrimes(n):
    isPrimes = [False]*2 + [True]*(n-1)
    for i in range(2, int(n**0.5)+1):
        if isPrimes[i]:
            for x in range(i*i, n+1, i):
                isPrimes[x] = False
    return isPrimes

X = int(input())

isPrimes = getIsPrimes(10**6)

for i in range(X, 10**6):
    if isPrimes[i]:
        print(i)
        break