\begin{problem}{Synonymous Words Number System }{standard input}{standard output}{2 seconds}{256 megabytes}

Synonymous Words Number System (SWNS) uses the lines of $N$ characters consisting of '0' and '1' ($2 \le N \le 10000$). There is only one operation with words within the number system -- it's called synonymization. Synonymization is reversing the character order in any substring containing even number of '1' symbols.

If we can create one word from the another one, by carrying out not more than $16 \cdot N$ synonymization, then such words are called synonyms.

It is necessary to determine whether the given words are synonymous, and, if so, find out the right sequence of synonymizations.



\InputFile
Different words with a length of $N$ characters are written in two lines, one per line.


\OutputFile
If the given words are not synonymous, output  'NO' in a single line. 

Otherwise, output 'YES' in the first line. The second line contains an integer $K$ ($K \le 16 \cdot N$) -- a number of synonymization required for the conversion. The following $K$ lines contain pairs of numbers that describe conversion of the first word into the second one. The first integer specifies a number of the first character participating in synonymization, and the second integer (always greater than the first one) -- a number of the last character.

\Examples

\begin{example}
\exmp{110001111
111100011
}{YES
1
3 7
}%
\exmp{110
010
}{NO
}%
\end{example}

\end{problem}

