Bilangan prima

Program detektor_bilangan_prima;
uses wincrt;
var a,b,c:integer;
begin
write('masukkan bilangan:');readln(a);
for b:= 1 to a do
begin
if (b = 2)or (b=3) or (b=7) or (b= 5)
or ((b-1>0) and (b mod 2 > 0) and (b mod 3>0) and (b mod 5>0) and (b mod 7>0)) then
writeln(b,' :Bilangan prima')
else
writeln(b,' :Bukan bilangan prima');
end;
end.