program songuyento;
uses crt;
var n,i,count : integer;
begin
clrscr;
write('Nhap so tu nhien n : ');
readln(n);
if ( n < 0 ) then 
begin
writeln('So nhap vao khong thoa man.');
write('Moi nhap lai: ');readln(n);
end;
count:=0;
for i:=1 to n do
begin
if ((n mod i) = 0 ) then count:=count+1;
end;
if ( count = 2 ) then write('So ',n,' la so nguyen to.');
else write('So ',n,' khong phai la so nguyen to.');
readln;
end.