import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] lreads(T = long)(long n){return generate(()=>readln.chomp.to!T()).take(n).array();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    long N = lread();
    auto D = aryread();
    auto cnt = new long[](13);
    cnt[0] = 1;
    foreach (d; D)
    {
        cnt[d]++;

        if (cnt[d] == 3 || ((d == 0 || d == 12) && cnt[d] == 2))
        {
            writeln(0);
            return;
        }
    }
    auto t = new bool[](24);
    t[0] = true;
    t[12] = (cnt[12] != 0);
    bool b;
    foreach (i; 1 .. 12)
    {
        if (cnt[i] == 1)
            t[(b ? 24 - i : i)] = true;
        if (cnt[i] == 2)
            t[24 - i] = t[i] = true;
        if (cnt[i] != 0)
            b = (b == false);
    }

    // writeln(t.map!(to!long));
    long ans = long.max;
    foreach (i; 0 .. 24)
        foreach (j; i + 1 .. 24)
            if (t[i] && t[j])
            {
                long diff = j - i;
                ans = min(ans, diff, 24 - diff);
            }
    writeln(ans);
}
