Let L1 = {aⁿbⁿa^m | m, n = 1, 2, 3 …………}
       L2 = {aⁿb^ma^m | m, n = 1, 2, 3 ……………}
       L3 = {aⁿbⁿaⁿ | n = 1, 2, 3 ………}