const
   n=10;
var
   str: array[1..n] of string;
   f1, f2: text;
   i, m: word;

function check(const strs:array of string; nn: word): boolean;
Var   tr: boolean; k: word;
begin
   tr:=true;
   for k:=1 to nn-1 do
      if(strs[k][1]<>strs[k-1][1]) then tr:=false;
   if tr then check:=true
      else
   check:=false;          
end;

Function sort_first(var strf: array of string; mm: word):string;
Var   fl: boolean; temp: string; j: word;
begin
   repeat
      fl:=false;
      for j:=0 to mm-2 do 
         if(strf[j][1]>strf[j+1][1]) then begin
            temp:=strf[j]; strf[j]:=strf[j+1]; strf[j+1]:=temp;
            fl:=true;
         end;
   until not (fl);
end;

begin
   Assign (f1, 'pasts.in');
   Assign (f2,'pasts.out');
   Reset (f1);
   Rewrite (f2);
   i:=1;
   while not(EoF(F1)) do begin
      read(F1, str[i]);
      inc(i);
   end;
   m:=i;
   if check(str, i) then begin
      for i:=m downto 1 do
         write(F2, str[i]);
   end
      else
   sort_first(str, m);
   write (f2,str[i]);
   
   Close (f1);
   Close (f2);
end.