[M, N] -> { S1[i0, i1, i2] -> [i0, i1, i2, 0] : i0 >= 1 and i1 >= 0 and i1 <= M and i1 <= i0 and i1 <= N - i0 and i2 >= 0 and i2 <= M and i2 <= i0 and i2 <= N - i0 }
[M, N] -> {  :  }
[M, N] -> { [i, j, k, l] -> separate[o0] }