#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

int main() {
	ll n;
	cin>>n;
	vector<ll> spf(n + 1);
    for(ll i=0;i<=n;i++) 
    	spf[i]=i;
    
	for(ll p=2;p<=sqrt(n);p++){
		if(spf[p]==p){
			for(ll i=p*p;i<=n;i=i+p){
				spf[i]=min(p, spf[i]);
			}
		}
	}
	cout<<spf[n];
	return 0;
}