Олимпиадный тренинг

Задача 37688. Memory training


Задача

Темы: Множества
Deniska decided to train Mishka's memory. To do this, he decided to name some numbers. And Mishka for each number must say the word YES, if this number was previously called Deniska or NO, if it was not called. Help Deniska train Mishka, write a program that would show what answer Mishka should pronounce.

Input
Enter a list of numbers. All numbers in the list are on the same line.

Imprint 
For each number, print the word YES (in a separate line) if this number has previously occurred in the sequence or NO if it has not.
 
Examples
# Input Output
1 1 2 3 2 3 4 NO
NO
NO
YES
YES
NO