Codeforces Round #397 by Kaspersky Lab and Barcelona bootcamp (div. 1 + div. 2 combined) B

Description

Kostya likes Codeforces contests very much. However, he is very disappointed, the He solutions is frequently hacked. That's why he decided to obfuscate (intentionally do less readable) his code before upcoming contest.

To obfuscate the code, Kostya first looks on the first variable name used in his program and replaces all its occurrences With a single symbol a, then he looks at the second variable name that have not been replaced yet, and replace s all it occurrences with b, and so on. Kostya is well-mannered, so he doesn ' t use any one-letter names before obfuscation. Moreover, there is at the most of the unique identifiers in his programs.

You is given a list of identifiers of some program with removed spaces and line breaks. Check If this program can be a result of Kostya ' s obfuscation.

Input

In the only line of input there is a string S of lowercase 中文版 letters (1?≤?| S|? ≤?500)-the identifiers of a program with removed whitespace characters.

Output

If This program can be a result of Kostya ' s obfuscation, print "YES" (without quotes), otherwise print "NO".

Examples input

Abacaba

Output

YES

input

Jinotega

Output

NO

Note

In the first sample case, one possible list of identifiers would is "numberstring number character number string numb Er ". Here are Kostya would obfuscate the program:

• Replace all occurences of number with A, the result would is "a string a character a string a",
• Replace all occurences of string with B, the result would is "a B a character a b a",
• Replace all occurences of character with C, the result would is "a B a c a B a",
• All identifiers has been replaced, thus the obfuscation is finished.

Test instructions: Someone tries to replace the variable name with a lowercase letter, replace the first variable name with a and the same variable from a, then replace the variable name with b instead of a, and so on, asking if the last given string is compliant

Solution: The first letter must be a, and then appear in turn b,c,d, recurrence is skipped, there is an interrupt description does not meet

1#include <bits/stdc++.h>2 using namespacestd;3 strings;4 intMain ()5 {6map<Char,int>Q;7map<Char,int>:: iterator it;8Cin>>s;9     if(s[0]!='a')Ten     { Onecout<<"NO"; A     } -     Else -     { the         intflag='a'; -          for(intI=0; I<s.length (); i++) -         { -             if((int) s[i]==flag) +             { -flag++; +q[s[i]]=1; A             } at             Else if(Q[s[i]]) -             { -                 Continue; -             } -             Else -             { incout<<"NO"; -                 return 0; to             } +         } -cout<<"YES"; the     } *     return 0; $}

Codeforces Round #397 by Kaspersky Lab and Barcelona bootcamp (div. 1 + div. 2 combined) B