fun int write_int(int x) = write(x)

fun [int] write_int_arr([int] x) = map(write_int, x)

fun int main() =
  let N = read(int) in
  let z = iota(N) in
  let w = write_int_arr(map(fn int (int x) => x + 2, z)) in
  let nl = write("\n") in
  write_int(reduce(op+, 0, w))