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Ural Regional School Programming Contest 2012

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A. Toxic Eruption

Time limit: 1.0 second
Memory limit: 64 MB
The world is in danger! African volcano “Love and Peace” suddenly erupted with superfluid and toxic lava that exterminates all life on its way and even corrodes iron and stones. That eruption has continued for a few days and no one can say when it would be over. Fortunately, military lab in one of the African countries had expected something like that, so they had started researches and developed top-secret defense that will save humanity. Unfortunately, this armor gets its magic safety properties only when its parts organize a closed figure (scientists say some electrical currents are guilty in that effect). It is a top new research, so it hasn’t the best behavior in all the situations. By now currents in closed figure appear only when parts of armor make right angles to each other and their ends are in close contact (it is simple to understand that only rectangles are safety figures).
Nevertheless that is the last chance of the humanity to survive. You have four large parts of armor of same width but possibly different length. And now the survival mission is in your hands: you are to make a conclusion, whether it is possible to build rectangle defense.


The only line of input contains integers a, b, c, d — length of armor parts (1 ≤ a, b, c, d ≤ 100).


If it is not possible to build rectangle defense, output “NO”, otherwise — “YES”.


3 3 4 2
3 3 4 4
Problem Author: Bulat Zaynullin
Problem Source: Ural Regional School Programming Contest 2012