Вычислить: P=a(a-n) (a-2n)*…*(a-n2)

var a, p:real;  n, i:integer; begin  write('a = ');  readln(a);  write('n = ');  readln(n);  p := a; for i := 1 to n do    p := p * (a - i * n);  writeln('p = ', p);  readln; end.