#include <stdio.h>
int zhishu(int n)//判断是否为质数
{
	int i;
	for (i = 2; i < n; i++)
	{
		if (n % i == 0)break;
	}
	if (i == n)return 1;
	else return 0;
}
int main()
{
	int n,i,j,ans;
	int c = 0;
	scanf("%d", &n);
	for (i = 1; i <= n; i++)
	{
		if(zhishu(i) == 1)
		for (j = n; j >= 1; j--)
		{
			if (zhishu(j) == 1)
			{
				c = i * j;
				if (c == n)break;
			}
		}
		if (c == n)break;
	}
	if (i >= j)ans=i;//取其中的最大值
	else ans = j;
	printf("%d",ans);
	return 0;
}