Program so_nguyen_to
Uses crt;
var i,n,dem:Integer;
Begin ClrScr;
write('Nhap so nguyen duong n');ReadLn(n);
dem:=0;
for i:= 1 to n do if n mod i=0 then dem:=dem+1;
if (n<2) or (dem<>2) then writeln(n,' khong phai la so nguyen to')
Else if dem=2 then writeln(n,' la so nguyen to');
Readln
End.