#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
int prime(int n){
	int i;
	for(i = n;i * i <= n;++i){
		if(n % i == 0){
			return 0;
		}
	}
	return n;
}
int main(){
	int n;
	int max = 0,sum = 0;
	cin>>n;
	for(int i = 2;i <= n;++i){
		if(n % i == 0){
			sum = prime(i);
			n = n / i;
		}
		if(max < sum){
			max = sum;
		}
	}
	cout<<max;
	return 0;
}