Rectangles

The Aizu Broadcasting Corporation's educational program (AHK Education) airs a children's craft program called "Ason de Tsukuro (Let's make something). Today's episode is about making rectangles with sticks, and we would like to see if we can make a rectangle using the four sticks prepared. However, we cannot cut or break the sticks.

You're given lengths of each stick, and your program must judge if you can create a rectangle which consists of all of them.

Input

Input is given in following format.

e1 e2 e3 e4

A line with integers e_i (1 ≤ e_i ≤ 100) which represents length of each stick.

Output

Output "yes" if we can create a rectangle, and 'no' if not. Do note squares are a kind of rectangles!

Sample Input 1

1 1 3 4

Sample Output 1

no

Sample Input 2

1 1 2 2

Sample Output 2

yes

Sample Input 3

2 1 1 2

Sample Output 3

yes

Sample Input 4

4 4 4 10

Sample Output 4

no

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