var t: array[0..255] of longint; s: string; i: longint; begin read(s); for i:=0 to 255 do t[i] := 0; for i:=1 to length(s) do inc(t[ord(s[i])]); for i:=1 to length(s) do if (t[ord(s[i])] = 1) then begin writeln(s[i]); exit; end; writeln('no'); end.
输入:xyzxyw
输出:1