A 42 -year old man was referred with a 2 week history of fever weakness and bleeding gum. Peripherial smear showed pancytopenia. The bone marrow examination revelaed 26% blasts frequently exhibiting Auer rods and mature myeloid cells. An occasional neutrophil with pseudo Pelger-Huet anomaly was also noted : Which of the following cytochemical stains is most likely to be positive ?