#P1411E. Poman Numbers
Poman Numbers
Description
You've got a string consisting of lowercase English letters from your friend. It turned out that this is a number written in poman numerals. The poman numeral system is long forgotten. All that's left is the algorithm to transform number from poman numerals to the numeral system familiar to us. Characters of are numbered from to from left to right. Let's denote the value of as , it is defined as follows:
- If , an arbitrary integer () is chosen, and it is defined that , where denotes the substring of from the -th to the -th position, inclusively.
- Otherwise , where is some English letter. Then , where is the position of letter in the alphabet (a, z).
Note that is chosen independently on each step.
Your friend thinks it is possible to get by choosing the right on every step. Is he right?
The first line contains two integers and (, ).
The second line contains a string consisting of lowercase English letters.
Print "Yes" if it is possible to get the desired value. Otherwise, print "No".
You can print each letter in any case (upper or lower).
Input
The first line contains two integers and (, ).
The second line contains a string consisting of lowercase English letters.
Output
Print "Yes" if it is possible to get the desired value. Otherwise, print "No".
You can print each letter in any case (upper or lower).
Note
In the second example, you cannot get . But you can get , for example, as follows:
- First choose , then abcabc
- a
- bcbc
- In the end abc