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There will need to be 25 blocks to build a up and down staircase with 5 steps up and down.
The reason is because I knew there will be 5 rows. I saw that for 2 ups and downs you have 3 for the second row. This got me thinking and I found the pattern. Add 2 more blocks to each row. You can use this strategy to build any up and down staircase. e.g: 7 ups and downs would be 36.