#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;
int n;
int ans=0;
int hei(int a,int b)
{
	int c=b%a;
	if(c==0)return 1;
	else return 0;
}
int main()
{
	freopen("prime.in","r",stdin);
	freopen("prime.out","w",stdout);
	scanf("%d",&n);
	bool is[n];
	int h=sqrt(n);
	memset(is,1,h);
	is[0]=is[1]=false;
	for(int i=2;i<=n;i++)
	  if(is[i]==true)
		for(int j=2;j<=n/i;j++)is[i*j]=false;
	for(int i=2;i<=n;i++)
	{
		if(hei(i,n)==1)
		  if(is[i]==true)ans=max(ans,n/i);
	}
    printf("%d",ans);
	fclose(stdin);
	fclose(stdout);
	return 0;
}