#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
//#include<>
using namespace std;
inline long long inin()
{
	long long yq=0;
	char y=getchar();
	long long q=1;
	for(;!isdigit(y);y=getchar()) if(y=='-') q=-1;
	for(;isdigit(y);y=getchar()) yq=(yq*10+y-'0');
	return yq*q;
}
bool is_prime(long long x)
{
	if(x<=1) return false;
	for(long long i=2;i*i<=x;i++)
	{
		if(x%i==0) return false;
	}
	return true;
}
int main()
{
	freopen("prime.in","r",stdin);
	freopen("prime.out","w",stdout);
	long long n=inin();
	for(long long i=n;i>=2;i--)
	{
		if(is_prime(i)&&n%i==0)
		{
			printf("%lld",i);
			return 0;
		}
	}
	return 0;
}