program Z462;
uses crt;
const s='abcdefghijklmnopqrstuvwxyz';
var a:char;

function  letter_or_not(var a:char):boolean;
      var i:integer;
      begin
          letter_or_not:=false;
          for i:=1 to length(s) do
          begin
              if a=copy(s,i,1) then letter_or_not:=true;
          end;
      end;