in C programming (explanation please) Thanks!

8.8 LAB: Nth from end or too small

Write a program that stores a list of positive integers from input into an array and outputs the Nth number from the end of the array. A negative integer indicates the end of the input and is not stored in the array. Convert the negative integer read at the end to positive and use as N. Output the negative integer read at the end if the size of the array is smaller than N. Assume the array will always contain fewer than 20 integers.

Ex: If the input is:

1 5 9 7 5 -3 

the output is:

9 

Ex: If the input is:

1 2 3 4 5 -6 

the output is:

-6 

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