var sz,s,letter:array[1..100000]of char;
    num,nm:array[1..100000]of integer;
    c:array[65..122]of longint;
    n,m,t,k,l,p,q:longint;
begin
     fillchar(c,sizeof(c),0);
     fillchar(nm,sizeof(nm),0);
     fillchar(num,sizeof(num),0);
     readln(n);
     m:=0;
     while not eof do
           begin
                inc(m);
                read(sz[m]);
                inc(c[ord(sz[m])]);
           end;
     l:=0;
     for t:=65 to 122 do
         begin
              for k:=1 to c[t] do
                  begin
                       inc(l);
                       letter[l]:=chr(t);
                       num[l]:=c[t]-k+1;
                  end;
         end;
     s[n-1]:=sz[m];
     nm[n-1]:=num[m];
     l:=n-1;
     for k:=1 to m-1 do
         begin
              inc(l);
              q:=l-1;
              if l=m+1 then
                 begin
                      l:=1;
                      q:=m;
                 end;
              p:=0;
              for t:=m downto 1 do
                  if sz[t]=s[q] then
                     begin
                       inc(p);
                       if p=nm[q] then
                       begin
                          s[l]:=letter[t];
                          nm[l]:=num[t];
                          break;
                       end;
                     end;
         end;
     for t:=1 to m do
         write(s[t]);
end.