是否有连续3个月

int[] year ={ 2005, 2005, 2005, 2005, 2005, 2005, 2007, 2007, 2007, 2008, 2008, 2009 };
        int[] mon ={ 1, 4, 6, 8, 9, 12, 1, 2, 6, 7, 8, 9 };
        bool a = false;
        string b = "";
        for (int i = 0; i < mon.Length; i++)
        {
            if (mon[i] == 11)
            {
                if (i + 2 < mon.Length && mon[i + 1] == 12 && (mon[i + 2] == 1 && year[i + 2] == year[i] + 1))
                {
                    a = true;
                    b = mon[i].ToString();
                    break;
                }
            }
            if (mon[i] == 12)
            {
                if (i + 2 < mon.Length && (mon[i + 1] == 1 && year[i + 1] == year[i] + 1) && (mon[i + 2] == 2 && year[i + 2] == year[i] + 1))
                {
                    a = true;
                    b = mon[i].ToString();
                    break;
                }

            }
            if (i + 2 < mon.Length && (mon[i] + 1 == mon[i + 1] && year[i] == year[i + 1]) && (mon[i] + 2 == mon[i + 2] && year[i] == year[i + 2]))
            {
                a = true;
                b = mon[i].ToString();
                break;
            }
        }
        if (a) Response.Write(b);