Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

Constraints

2 ≤ |S| ≤ 26, where |S| denotes the length of S.

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If all the characters in S are different, print yes (case-sensitive); otherwise, print no.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

Solution in Pascal (FPC 2.6.2) (judge verdict: Accepted)

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils,Classes;
var
  h,w,i,j,count,x,y,m,n,c,a,b,min:Integer;
  //a:array of string;
  s,s1,s2,s3:string;
  sw:char;
  tf:Boolean;
  nyu:TStringList;
begin
  try
    { TODO -oUser -cConsole Main : ここにコードを記述してください }
    Readln(s);

    for i := 1 to Length(s) do begin
      min := i;
      for j := i+1 to Length(s) do begin
        if s[j] < s[min] then
        min := j;
      end;
      sw:=s[i];
      s[i]:=s[min];
      s[min]:=sw;
    end;

    for i := 1 to Length(s) - 1 do
      if s[i]=s[i+1] then begin
        Writeln('no');
        Readln;
        exit;
      end;

    Writeln('yes');
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.