#include <bits/stdc++.h>
using namespace std;
#define N 10000000
bool P[N + 1];
void eratos() {
	for (int i = 0; i <= N; i++)
		P[i] = true;
	P[0] = P[1] = false;
	for (int i = 2; i * i <= N; i++)
		if (P[i])
			for (int j = 2; i * j <= N; j++)
				P[i * j] = false;
}
int getQuads(int n) {
	for (int i = n; i >= 13; i--)
		if (P[i] && P[i - 2] && P[i - 6] && P[i - 8])
			return i;
}
int main() {
	eratos();
	int n;
	while (cin >> n && n)
		cout << getQuads(n) << endl;
	return 0;
}