fix(02): fixed code
fix(02): fixed code

fpvandoorn/tutorial,avigad/tutorial,Hodapp87/cs6460_project,Hodapp87/cs6460_project,avigad/tutorial,cjmazey/fork_leanprover_tutorial,fpvandoorn/tutorial,Hodapp87/cs6460_project,fpvandoorn/tutorial,cjmazey/fork_leanprover_tutorial,leanprover/tutorial,avigad/tutorial,soonhokong/lean-tutorial,soonhokong/lean-tutorial,leanprover/tutorial,leanprover/tutorial,cjmazey/fork_leanprover_tutorial,soonhokong/lean-tutorial