The contradiction arises when the four statements are combined for the case that the fourth statement is true, the corresponding round we define as to be round formula_77. Therefore, in round formula_77 of the experiment, formula_39measures formula_76 and knows that formula_37measures formula_76 as well. The latter part then implies that formula_39knows that formula_38 had measured formula_91, which implies that formula_39 knows that formula_36 got formula_46 which in turn implies that formula_39 knows that he himself will measure formula_89, and hence a contradiction appears.