bài 1

program bai1;
var kt:boolean;
      so,i,x:integer;
begin
writeln('xac dinh so nguyen to');
writeln(' vd: 2,3,5,7,11,13,17,19...');
writeln(' nhap so bat ki:');
readln(so);
if so>=2 then
kt:=(true);
for i:=2 to so-1 do if so mod i = 0 then kt:=false;
if kt then writeln(' day la so nguyen to ', so)
else writeln('day khong phai la so nguyen to ', so);
readln;
end.