10 prisoners are about to be executed. The executioner gives them each a chance to survive, "I will place a little hat on each of your heads, either black or white. All those who can correctly guess the color of the hat they are wearing will be let off, and all those who can't will be killed instantly." Before they enter the execution room, they are given a chance to say their final prayers together. After the prayers, they are lined up all facing in a direction, such that the last man can see all the 9 men ahead of him, and the 1st man can only see a wall. Then, the hats are placed on the prisoners, and the executioner first attends to the last guy in the line. During the prayers, 1 of the prisoners came up with a brilliant strategy to ensure maximum survival. The big question: What is the best strategy such that a maximum number of prisoners will SURELY survive?