context-free pumping lemma a^n b^n c^n Human 3 aaabbbccc 2 2 1 1 1 U = aa; V = a; X = b; Y = b; Z = bccc; I = 2; <i>Failed</i> 2 1 1 1 2 0 1 0 1 -1 1 1 0 2 -1 2 2 0 1 -1 3 1 0 1 -1 4 1 0 2 -1 5 1 0 1 -1 5 2 0 1 -1 6 1 0 1 -1 6 0 1 1 -1 6 1 0 0 -1