Description

Permutation and combination are common mathematical methods. A combination means selecting $r$ elements from $n$ elements (order does not matter and $r \le n$). We can simply think of the $n$ elements as the natural numbers $1, 2, \dots, n$, and choose any $r$ numbers from them.

You are required to output all combinations.

For example, when $n=5, r=3$, all combinations are:

$123,124,125,134,135,145,234,235,245,345$.

Input Format

A single line with two natural numbers $n, r$ ($1 < n < 21$, $0 \le r \le n$).

Output Format

Output all combinations. Each combination occupies one line, and the elements in it are sorted in ascending order. Each element occupies a field width of three characters. All combinations are in lexicographical order.

Note: When outputting, each number must have a field width of $3$. In C++, you can use the following code:

cout << setw(3) << x;

This outputs a number $x$ with a field width of $3$. Note that you need the header file iomanip.

5 3 

  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

Hint

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