#include <iostream>
#include <algorithm>
#include <vector>
#include <deque>
#include <string>
#include <tuple>
#include <functional>
#include <numeric>
#include <cmath>
#include <iomanip>
#include <map>
#include <random>
//#include "toollib.h"
#define INT_MAX 2147483647
#define Loop(i, n) for(int i = 0; i < (int)n; i++)
#pragma warning (disable:4018)

using namespace std;
typedef long long int lint;

//***** Main Program *****
int main() {
	lint N;
	cin >> N;
	if (N % 3 == 0) cout << 3 << endl;
	else if (N % 4 == 0) cout << 4 << endl;
	else if (N % 5 == 0) cout << 5 << endl;
	else {
		for (lint i = 7; i < N; i = i + 2) {
			if (N%i == 0) {
				cout << i << endl;
				break;
			}
		}
	}
	return 0;
}