Function ngto(a: qword): boolean; Var i: longint; Begin If a<2 then exit(false); For i:=2 to a div 2 do If a mod i = 0 then exit(false); exit(true); End;
Begin Clrscr; Write('Nhap n: '); Readln(n); If ngto(n) then Write('YES') Else Write('NO'); Readln End.
