var i,n: longint;
begin
    write('Nhap so i: ');
    readln(i);
    if ((i=1) or (i=0)) then writeln('Day khong phai la so nguyen to')
    else
    begin
        for n:=2 to trunc(sqrt(i)) do
            if (i mod n = 0) then 
            begin   
                writeln('Day khong phai la so nguyen to');
                break;
            end;
        if (n = trunc(sqrt(i))) then writeln('Day la so nguyen to');
    end;
    readln
end.

$\text{uses crt;}$

$\text{var n,i:integer;}$

$\text{kt:boolean;}$

$\text{begin}$

$\text{clrscr;}$

$\text{writeln('nhap vao so n:');}$

$\text{readln(n);}$

$\text{kt:=true;}$

$\text{if n<2 then kt:=false;}$

$\text{for i:=2 to n-1 do}$

$\text{if n mod i=0 then kt:=false;}$

$\text{if kt then writeln('la so nguyen to')else }$

$\text{writeln('khong phai la so nguyen to');}$

$\text{readln}$

$\text{end.}$