#include<fstream>
#include<math.h>
using namespace std;
ifstream in("numar2.in");
ofstream out("numar2.out");
bool palindrom(int x)
{
	int q=x,inv=0;
	while(q)
	{
		inv=inv*10+q%10;
		q/=10;
	}
	if(inv==x)
		return true;
	return false;
}
bool cub(int x)
{
    int root(round(cbrt(x)));
    return x == root * root * root;
}

int main()
{
	int n,j;
	in>>n;
	for(j=n;j>1;j--)
		if(palindrom(j) && cub(j))
			out<<j,exit(0);
	return 0;
}