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1-step staircase needs 1 cube (1 x 1 = 1)
2-step staircase needs 4 cubes (2 x 2 = 4)
3-step staircase needs 9 cubes (3 x 3 = 9)
4-step staircase needs 16 cubes (4 x 4 = 16)
5-step staircase needs 25 cubes (5 x 5 = 25)

so any staircase will need the number of cubes that is the square of the number of steps going either up or down.

Pattern: Number of cubes needed = square number of steps