CF720A Closing ceremony

The closing ceremony of Squanch Code Cup is held in the big hall with $ n×m $ seats, arranged in $ n $ rows, $ m $ seats in a row. Each seat has two coordinates $ (x,y) $ ( $ 1

The first line of input contains two integers $ n $ and $ m $ ( $ 1

If it is possible to distribute tickets between people in the described manner print "YES", otherwise print "NO".