#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<valarray>
//#include<bits/stdc++.h>
//using namespace std;
using namespace std;

int main(){
	int n;
	scanf("%d", &n);
	for (int i = n - 100; i <= n + 100; i++){
		for (int j = 2; j < i; j++){
			if (i % j == 0){
				printf("%d\n", i);
				return 0;
			}
		}
	}
	puts("-1");
	return 0;
}