program ktnt;
uses crt;
var a,i,n: integer;
begin
clrscr; a:=0;
write('Nhap so can kiem tra:'); readln(n);
for i:=1 to n do if n mod i = 0 then a:=a+1;
if (a <> 2) or (n<=1) then writeln(n,' khong phai la so nguyen to') else writeln(n,' la so nguyen to');
readln
end.