Generate Unique Rounds

Given a total number of available problems m and an integer k representing the number of problems required for a round, along with a list of m unique problem IDs, your task is to generate all possible unique rounds. Each round is a combination of k problem IDs, and the IDs within each round must be in ascending order. The rounds should be output in lexicographical order.

If k > m, then no valid round exists; in that case, output No valid rounds.

The number of rounds can be computed using the combinatorial formula: \( C(m,k)=\frac{m!}{k!(m-k)!} \).

inputFormat

The input is read from standard input (stdin) and consists of two lines:

• The first line contains two integers m and k separated by a space.
• The second line contains m space-separated integers representing the problem IDs.

outputFormat

If valid rounds can be formed, output each round on a new line with the problem IDs separated by a single space. If no valid round exists (i.e. when k > m), output No valid rounds.

## sample

5 3
1 2 3 4 5

1 2 3
1 2 4
1 2 5
1 3 4
1 3 5
1 4 5
2 3 4
2 3 5
2 4 5
3 4 5

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