//C++

#include <iostream>
using namespace std;

int main(){
	int n;
	bool prim;
	cin >> n;
	prim = false;
	while(! prim){
		n++;
		prim = true;
		if(n<2)
			prim = false;
		if(n % 2 == 0 && n > 2)
			prim = false;
		for(int d = 3 ; d * d <= n ; d += 2)
			if(n % d == 0)
				prim = false;

	}
	cout << n;
	return 0;
}



//Python

def primality(n):
    if n < 2:
        return False
    if n < 4:
        return True
    if n % 2 == 0:
        return False
    i = 3
    while i * i <= n:
        if n % i == 0:
            return False
        i += 2
    return True

x = int(raw_input())
done = False
i = x + 1
while done == False:
    if primality(i) == True:
        print(i)
        done = True
    i += 1