Crowded Carriage Capacity

A train has a maximum capacity of n passengers overall, which means each carriage's capacity will share an equal proportion of the maximum capacity.

Create a function which returns the index of the first carriage which holds 50% or less of its maximum capacity. If no such carriage exists, return -1.

Worked Example

find_a_seat(200, [35, 23, 18, 10, 40]) ➞ 2

# There are 5 carriages which each have a maximum capacity of 40 (200 / 5 = 40).
# Index 0's carriage is too full (35 is 87.5% of the maximum).
# Index 1's carriage is too full (23 is 57.5% of the maximum).
# Index 2's carriage is good enough (18 is 45% of the maximum).
# Return 2.

Examples

find_a_seat(20, [3, 5, 4, 2]) ➞ 3

find_a_seat(1000, [50, 20, 80, 90, 100, 60, 30, 50, 80, 60]) ➞ 0

find_a_seat(200, [35, 23, 40, 21, 38]) ➞ -1

Notes

• This means if a train can hold 200 passengers, and has 5 carriages, then that means each carriage can hold a maximum of 40 passengers each.
• All carriage numbers will be positive integers, which will be able to divide evenly.
• Remember to return -1 if no carriage is empty enough.