[STATEMENT]
lemma setdiff_diff_insert: "A-B-C=D-E-F \<Longrightarrow> insert m (A-B-C) = insert m (D-E-F)"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. A - B - C = D - E - F \<Longrightarrow> insert m (A - B - C) = insert m (D - E - F)
[PROOF STEP]
by simp