Program if then else

Source codenya :

program angkalulus;
uses wincrt;
var
nilai : integer;

begin
writeln('------------------------------');
writeln('         Program Nilai               ');
writeln('------------------------------');
writeln;
write('masukkan nilai anda : ');readln(nilai);
writeln;
write('Keterangan : ');

if ((nilai <=100) and (nilai>80)) then
write('A')
else if ((nilai <=80) and (nilai>70)) then
write('B')
else if ((nilai <=70) and (nilai>60)) then
write('C')
else if ((nilai <=60) and (nilai >50)) then
write('D')
else
write('E');
end.