CF884B Japanese Crosswords Strike Back

A one-dimensional Japanese crossword can be represented as a binary string of length $ x $ . An encoding of this crossword is an array $ a $ of size $ n $ , where $ n $ is the number of segments formed completely of $ 1 $ 's, and $ a_{i} $ is the length of $ i $ -th segment. No two segments touch or intersect. For example: - If $ x=6 $ and the crossword is $ 111011 $ , then its encoding is an array $ {3,2} $ ; - If $ x=8 $ and the crossword is $ 01101010 $ , then its encoding is an array $ {2,1,1} $ ; - If $ x=5 $ and the crossword is $ 11111 $ , then its encoding is an array $ {5} $ ; - If $ x=5 $ and the crossword is $ 00000 $ , then its encoding is an empty array. Mishka wants to create a new one-dimensional Japanese crossword. He has already picked the length and the encoding for this crossword. And now he needs to check if there is exactly one crossword such that its length and encoding are equal to the length and encoding he picked. Help him to check it!

The first line contains two integer numbers $ n $ and $ x $ ( $ 1

Print YES if there exists exaclty one crossword with chosen length and encoding. Otherwise, print NO.