CF1411E.Poman Numbers

普及/提高-

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题目描述

You've got a string SS consisting of nn 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 SS are numbered from 11 to nn from left to right. Let's denote the value of SS as f(S)f(S) , it is defined as follows:

  • If S>1|S| > 1 , an arbitrary integer mm ( 1m<S1 \le m < |S| ) is chosen, and it is defined that f(S)=f(S[1,m])+f(S[m+1,S])f(S) = -f(S[1, m]) + f(S[m + 1, |S|]) , where S[l,r]S[l, r] denotes the substring of SS from the ll -th to the rr -th position, inclusively.
  • Otherwise S=cS = c , where cc is some English letter. Then f(S)=2pos(c)f(S) = 2^{pos(c)} , where pos(c)pos(c) is the position of letter cc in the alphabet ( pos(pos( a )=0) = 0 , pos(pos( z )=25) = 25 ).

Note that mm is chosen independently on each step.

Your friend thinks it is possible to get f(S)=Tf(S) = T by choosing the right mm on every step. Is he right?

输入格式

The first line contains two integers nn and TT ( 2n1052 \leq n \leq 10^5 , 1015T1015-10^{15} \leq T \leq 10^{15} ).

The second line contains a string SS consisting of nn lowercase English letters.

输出格式

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).

输入输出样例

  • 输入#1

    2 -1
    ba

    输出#1

    Yes
  • 输入#2

    3 -7
    abc

    输出#2

    No
  • 输入#3

    7 -475391
    qohshra

    输出#3

    Yes

说明/提示

In the second example, you cannot get 7-7 . But you can get 11 , for example, as follows:

  1. First choose m=1m = 1 , then f(f( abc )=f() = -f( a )+f() + f( bc ))
  2. f(f( a )=20=1) = 2^0 = 1
  3. f(f( bc )=f() = -f( b )+f() + f( c )=21+22=2) = -2^1 + 2^2 = 2
  4. In the end f(f( abc )=1+2=1) = -1 + 2 = 1
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