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)

n = int(input())
x = 10**6
li = [True for i in range(x+10)]
li[0] = False
li[1] = False

for i in range(int(x**0.5)+1):
    if li[i]:
        m = 2
        while(i*m<=x):
            li[i*m] = False
            m += 1
#print(li)
for i in range(x):
    if i>=n and li[i]:
        print(i)
        break