Kata

Raj was to move up through a pattern of stairs of a given number (n). Help him to get to the top using the function stairs.

##Keep in mind :

• If n<1 then return ' ' .
• There are a lot of spaces before the stair starts except for pattern(1)

##Examples : pattern(1)

      1 1

pattern(6)

                      1 1
                  1 2 2 1  
              1 2 3 3 2 1
          1 2 3 4 4 3 2 1
      1 2 3 4 5 5 4 3 2 1
  1 2 3 4 5 6 6 5 4 3 2 1

pattern(12)

                                              1 1
                                          1 2 2 1
                                      1 2 3 3 2 1
                                  1 2 3 4 4 3 2 1
                              1 2 3 4 5 5 4 3 2 1
                          1 2 3 4 5 6 6 5 4 3 2 1
                      1 2 3 4 5 6 7 7 6 5 4 3 2 1
                  1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1
              1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1
          1 2 3 4 5 6 7 8 9 0 0 9 8 7 6 5 4 3 2 1
      1 2 3 4 5 6 7 8 9 0 1 1 0 9 8 7 6 5 4 3 2 1
  1 2 3 4 5 6 7 8 9 0 1 2 2 1 0 9 8 7 6 5 4 3 2 1