#include <iostream>
#include <algorithm>
#include <vector>
#include <set>

int n;
std::vector<bool> pr(10000001, true);
std::set<int> sets;

int main() {
    for(int i = 2; i <= 10000000; ++i) {
        if(pr[i]) {
            for(long long j = ((long long)i) * i; j <= 10000000ll; j += i) {
                pr[j] = false;

            }
            if(i >= 13) {
                if(pr[i - 2] && pr[i - 6] && pr[i - 8]) {
                    sets.insert(i);
                }
            }
        }
    }

    while(std::cin >> n, n) {
        std::set<int>::iterator it  = sets.upper_bound(n);
        --it;

        std::cout << *it << std::endl;
    }
}