var
i, j, n, r, c, d : longint;
begin
readln(n, r);
c := 0;
for i := 1 to n do begin
d := 1;
for j := 1 to i do begin
d := d * r;
end;
inc(c, d);
end;
writeln(c);
end.

Jika diberi input 20 2, maka outputnya adalah?
a. 1048576
b. 2097152
c. 1048575
d. 2097150
e. 2097151