A. Words
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Professor Oak has two words of length $$$n$$$, $$$a_{1}$$$ and $$$a_{2}$$$. Both words are made up of lowercase letters from a to z. Some of the letters are unreadable, and the professor has replaced them with a $$$?$$$.

The professor wonders if it is possible to replace the $$$?$$$ with lowercase letters so that the word $$$a_{1}$$$ is strictly lexicographically smaller than $$$a_{2}$$$.

Input

The input consists of several cases.

Each case starts with an integer $$$n$$$ followed by the words $$$a_{1}$$$ and $$$a_{2}$$$.

Output

For each case, write a line with the answer 'si' if it is possible and 'no' otherwise.

Scoring

The sum of all $$$n$$$ is less than 10,000,000.

Example
Input
2
ib
?b
5
pbi?v
pbiav
Output
si
no