// yukicoder: No.312 置換処理
// 2019.4.19 bal4u

#include <stdio.h>
#include <math.h>

//// 素数テスト
long long calc_pow(int a, long long k, long long n)
{
	long long p;
	unsigned long long bit;

	p = 1;
	for (bit = 0x8000000000000000U; bit > 0; bit >>= 1) {
		if (p > 1) p = (p*p) % n;
		if (k & bit) p = (p*a) % n;
	}
	return p % n;
}

int suspect(int b, long long n)
{
	int i, t;
	long long u, n1;
	long long x0, x1;

	u = n1 = n - 1;
	t = 0;
	while ((u & 1) == 0) {
		t++;
		u >>= 1;
	}
	x0 = calc_pow(b, u, n);
	for (i = 1; i <= t; i++) {
		x1 = (x0*x0) % n;
		if (x1 == 1 && x0 != 1 && x0 != n1) return 0;
		x0 = x1;
	}
	return x1 == 1;
}

int prime_test(long long n)
{
	if (n == 1) return 0;          /* 1 */
	if (n == 2 || n == 3) return 1;          /* 2, 3 */
	if ((n & 1) == 0) return 0;  /* other even integers */
	if (!suspect(2, n)) return 0;
	if (n <= 1000000) {
		if (!suspect(3, n)) return 0;
	}
	else {
		if (!suspect(7, n)) return 0;
		if (!suspect(61, n)) return 0;
	}
	return 1;
}

int main()
{
	int b, a;
	long long N, ans;

	scanf("%lld", &N);
	if (N % 3 == 0) ans = 3;
	else if ((N & 3) == 0) ans = 4;
	else {
		ans = N;
		if ((N & 1) == 0) N >>= 1, ans = N;
		if (!prime_test(N)) {
			b = (int)sqrt((double)N);
			for (a = 5; a <= b; a++) {
				if (N % a == 0) break;
			}
			if (a <= b) ans = a;
		}
	}
	printf("%lld\n", ans);
	return 0;
}