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.

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