#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#define rep(i,l,n) for(int i=l;i<n;i++)
#define rer(i,l,n) for(int i=l;i<=n;i++)
#define all(a) a.begin(),a.end()
#define o(a) cout<<a<<endl
#define pb(a) push_back(a)
#define mk(a,b) make_pair(a,b)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

int main(){
	lint n,ans=3;
	cin>>n;
	for(int i=3;i*i<=n;i++){
		if(n%i==0){
			ans=i; break;
		}
	}
	o(ans);
}