while trade favorite exchange trader William realize found vulnerability use vulnerability change value certain internal variable advantage to play decide change value internal variable a_1 a_2 ldot a_n a_1 a_2 ldot a_n for unknown reason number service variable numberWilliam understand action attract attention exchange security team number action exceed 5000 operation variable absolute value great 1018 William perform action type choose variable indice j j Perform assignment a_i a_i a_j perform assignment a_j a_j a_i William want develop strategy internal variable desire value