A9554 | Choosing Teams

The Saratov State University Olympiad Programmers Training Center (SSU OPTC) has $n$ students. For each student you know the number of times he/she has participated in the ACM ICPC world programming championship. According to the ACM ICPC rules, each person can participate in the world championship at most 5 times.

The head of the SSU OPTC is recently gathering teams to participate in the world championship. Each team must consist of exactly three people, at that, any person cannot be a member of two or more teams. What maximum number of teams can the head make if he wants each team to participate in the world championship with the same members at least $k$ times?

The first line contains two integers, $n$ and $k$ $(1<=n<=2000; 1<=k<=5)$ . The next line contains $n$ integers: $y_{1},y_{2},...,y_{n}$ $(0<=y_{i}<=5)$ , where $y_{i}$ shows the number of times the $i$ -th person participated in the ACM ICPC world championship.

Print a single number — the answer to the problem.