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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
#define QWQ puts("successfully enter.")
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,n) for(int i=1;i<=n;i++)
#define FILL(a,val) memset(a,val,sizeof(a))
int n;
void display(initializer_list<int> out)
{
	cout<<"DISPLAY:";
	for(auto x:out) cout<<x<<' ';
	puts("");
}
bool isprime(int p)
{
	if(p<2) return false;
	for(int i=2;i*i<=p;i++)
		if(p%i==0)
			return false;
	return true;
}
int main()
{
	cin>>n;
	for(int i=n;;i++)
		if(isprime(i))
		{
			cout<<i;
			return 0;
		}
	return 0;
}