Tall People

Create a function that takes a 2D array as an argument and returns the number of people whose view is blocked by a tall person. The concert stage is pointed towards the top of the 2D array and the tall person (represented by a 2) blocks the view of all the people (represented by a 1) behind them.

Examples

block([
  [1, 1, 1, 1, 1],
  [1, 1, 1, 1, 1],
  [1, 1, 1, 1, 2],
  [1, 1, 1, 1, 1],
  [1, 1, 1, 1, 1]
]) ➞ 2

# The tall person blocks 2 people behind him thus
# the function returns 2.

block([
  [1, 2, 1, 1],
  [1, 1, 1, 2],
  [1, 1, 1, 1],
  [1, 1, 1, 1],
]) ➞ 5

# There are 2 tall people that block everyone behind
# them. The first tall person in the first row blocks 3
# people behind him while the second tall person in
# the second row blocks 2 people behind him thus the
# function returns 5.

block([
  [1, 1, 1, 1],
  [2, 1, 1, 2],
  [1, 1, 1, 1],
  [1, 1, 1, 1],
]) ➞ 4

Notes

1. There is only a maximum of 1 tall person in every column.
2. No view is blocked if the tall person is in the last row.