50 red lights are arranged in a row and numbered in order, 1, 2, 3, 4, ... 50, each light is equipped with a button, as long as you press the button, the red light will turn into a green light, and press the green light again It turned into a red light again, and there were 50 people. The first person came over and pressed the button for every number that was a multiple of 1, then the second person pressed the button for every number that was a multiple of 2, and the third person pressed the button for every number that was a multiple of 2. Press the button that is a multiple of 3, and continue like this... When the 50th person comes over, press the button that is a multiple of 50, then how many lights are red lights at the end.
50盏红灯排成一排，按顺序分别编成号码，1，2，3，4，…50，每盏灯装有按钮，只要一按按钮，红灯就变成绿灯，再一按绿灯又变成了红灯，有50个人，第一个人走过来把凡是号码1的倍数的按钮按一下，接着第二个人把凡是号码为2的倍数的按钮按一下，第三个人把号码为3的倍数的按钮按一下，这样继续下去，…当第50个人走过来，把号码为50的倍数的按钮按一下，那么最后有多少盏灯是红灯．
<gadget id="calculator">50 - 7</gadget>
<output>43</output>

<result>43</result>