Lời giải :
program hotrotinhoc;
var a,b,s : integer;
function (s: longint) : boolean;
var a,s : longint;
begin
kt:=false;
if s=a*b then kt:=true;
end;
begin
write('chieu dai la:'); readln(a);
write('chieu rong la:'); readln(b);
if kt=true then write(s);
readln
end.