1[n] -> { [i0, i1] -> (((4 * n - n^2) + (-3/2 + 2 * n) * i0 - 1/2 * i0^2) - i1) : i1 >= -1 + 3n - i0 and i1 >= -1 + 2n - i0 and i0 >= 0 and i1 <= -2 + 4n - i0 and i0 <= -2 + 4n and i0 <= -1 + 3n and i1 >= 0 and i1 <= -1 + n } 2