#include <bits/stdc++.h>
using namespace std;
using Int = int_fast64_t;

Int n, ans = 1e9;
vector<Int> a(1, 0);
vector<Int> b(24);

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cin >> n;
	for(Int i=0; i<n; ++i){
		Int t; cin >> t;
		a.push_back(t);
	}
	sort(a.begin(), a.end());
	for(size_t i=0; i<a.size(); ++i){
		if(i % 2 == 0){
			if(b[a[i]] > 0){
				cout << 0 << "\n";
				return 0;
			}else{
				++b[a[i]];
			}
		}else{
			if(b[(24-a[i])%24] > 0){
				cout << 0 << "\n";
				return 0;
			}else{
				++b[24-a[i]];
			}
		}
	}
//	for(Int i=0; i<24; ++i) cout << i << " " << b[i] << "\n";
	for(Int i=0; i<23; ++i)
		for(Int j=i+1; j<24; ++j)
			if(b[i] & b[j])
				ans = min({ans, j-i, 24-j});
	cout << ans << "\n";
}