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>
#define int long long
using namespace std;
int pr[1000005];
int vis[1000005];
signed main()
{
    int x;
    cin>>x;
    for(int i=2;i<=1000000;i++)
    {
        if(vis[i]==0)
        {
         pr[i]=1;   
        for(int j=i;j<=1000000;j+=i)
        {
            vis[j]=1;
        }
        }
    }
    
    for(int i=x;;i++)
    {
        if(pr[i])
        {
            cout<<i;
            return 0;
        }
    }
    return 0;
}