为什么0分？

var n,i,j,x,y:longint;
function pd(a:longint):boolean;
begin
  for j:=2 to trunc(sqrt(a)) do
   if a mod j=0 then exit(false);
     exit(true);
end; 
begin
  readln(n);
  for x:=2 to n-1 do
   if pd(x) then begin
    for y:=2 to n-1 do
     if pd(y)then if pd(n-x-y) then begin 
       write(x,y,n-x-y);
       halt;
       end;
    end;
end.