You are required to find the proper sequence of the four sentences S1: A mighty popular Revolt broke out in Northern and Central India in 1857 S6: Millions of peasants, artisans and soliders fought heroically and wrote a glorious chapter. P: Sepoys, or the Indian soliders of the Company's army Q：but soon engulfed wide regions and involved the masses R: and nearly swept away the British rule S: It began with a mutiny