#include "bits/stdc++.h"
using namespace std;

int main() {
	int N, D, X[13] = {}, ANS = 24;
	vector<int> V;
	bool L = true, R = true, Y[24] = {};
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> D;
		X[D]++;
	}
	if (X[0] != 0) {
		cout << 0;
		return 0;
	}
	for (int i = 1; i < 12; i++) {
		if (X[i] > 2) {
			cout << 0;
			return 0;
		}
		if (X[i] == 2) {
			Y[i] = true, Y[24 - i] = true;
			L = true, R = true;
		}
		if (X[i] == 1) {
			if (L) {
				Y[i] = true;
				L = false, R = true;
			}
			else {
				Y[24 - i] = true;
				L = true, R = false;
			}
		}
	}
	if (X[12] > 1) {
		cout << 0;
		return 0;
	}
	if (X[12] == 1) Y[12] = true;
	V.push_back(0);
	for (int i = 0; i < 24; i++) {
		if (Y[i]) V.push_back(i);
	}
	V.push_back(V[0] + 24);
	for (int i = 0; i < V.size() - 1; i++) {
		ANS = min(ANS, V[i + 1] - V[i]);
	}
	cout << ANS;
}