How to print every third line of some text input by user from keyboard?

Question

So basically this is the specific question:

Write a Python program that reads input from the keyboard (standard input). The input will consist of some number of lines of text. The input will be terminated by a blank line. Your program should print every third line.

For instance, if the input is the following:

Answer 1

You can take input using input() function and check blank line checking the line is empty string or not

i = 1
while 1:
    line = input()
    if line=='':
        break
    if i%3 == 0:
        print(line)
    i = i+1