#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define x first
#define y second

using namespace std;

typedef long double ld;
typedef long long ll;

const int MAX_BOUND = (int) 1e6;

int main()
{
 	//freopen("input.txt", "r", stdin);
 	//freopen("output.txt", "w", stdout);
	ios_base::sync_with_stdio(0); cin.tie(0);

	ll x;
	cin >> x;
	if (x == 1) cout << "1\n", exit(0);

	for (int i = 2; i <= MAX_BOUND; i++)
	{
	 	ll cur = i;
	 	int step = 1;
	 	while (cur < x) cur *= i, step++;

	 	if (cur != x) continue;

	 	int divis = 0;
	 	for (int j = 1; j * j <= i; j++)
	 	{
	 	 	if (i % j != 0) continue;
	 	 	divis++;
	 	 	if (j != i / j) divis++;
	 	}
	 	
	 	if (divis == step) cout << i << '\n', exit(0);
	}

	ll sq = sqrtl(x);
	while (sq * sq > x) sq--;
	while ((sq + 1) * (sq + 1) <= x) sq++;

	bool is_prime = true;
	for (int i = 2; i * i <= sq; i++)
		if (sq % i == 0) is_prime = false;

	if (sq * sq == x && is_prime) cout << sq << '\n', exit(0);
	
	cout << "-1\n";
	return 0;
}