| # A = # A0, m < # A0, m < i, i + 1 < # A0, perm(A[m + 1, y][2 + m, x], A0), sorted(A, 0, m + 1), sorted(A, 3 + m, i + 2), i ≤ # A0, m + 1 ≠ i → x < A[3 + m], m + 1 ≠ i → ¬ A[3 + m] < A[m] ⊦ x < A[m], x < y, sorted(A[2 + m, x], 2 + m, i + 2) ∧ perm(A[2 + m, x][m + 1, y], A0) |
# A = # A0, i + 1 < # A0, m < i, m < # A0, perm(A[m + 1, y][2 + m, x], A0), sorted(A, 3 + m, i + 2), sorted(A, 0, m + 1), i ≤ # A0, m + 1 ≠ i → ¬ A[3 + m] < A[m], m + 1 ≠ i → x < A[3 + m] ⊦ x < y, x < A[m], sorted(A[2 + m, x], 2 + m, i + 2)
# A = # A0, i + 1 < # A0, m < i, m < # A0, perm(A[m + 1, y][2 + m, x], A0), sorted(A, 3 + m, i + 2), sorted(A, 0, m + 1), i ≤ # A0, m + 1 ≠ i → ¬ A[3 + m] < A[m], m + 1 ≠ i → x < A[3 + m] ⊦ x < y, x < A[m], perm(A[2 + m, x][m + 1, y], A0)