Solve problem "Has the number been encountered before" online - Learn Python 3 - Snakify

Has the number been encountered before


Given a sequence of numbers, determine if the next number has already been encountered. For each number, print the word YES (in a separate line) if this number has already been encountered, and print NO, if it has not already been encountered.

In all the problems input the data using input() and print the result using print().