Write a series of natural numbers 1, 2, ..., 98, 99 on the paper. One operation refers to crossing out the first three numbers in the sequence, and then writing the sum of these three numbers at the end of the sequence. For example, 4, 5, ..., 98, 99, 6 are obtained after the first operation; and 7, 8, ..., 98, 99, 6, 15 are obtained after the second operation. Going on like this, there will be only one number left in the end, what is the number left in the end?
在纸上写着一列自然数1，2，…，98，99．一次操作是指将这列数中最前面的三个数划去，然后把这三个数的和写在数列的最后面．例如第一次操作后得到4，5，…，98，99，6；而第二次操作后得到7，8，…，98，99，6，15．这样不断进行下去，最后将只剩下一个数，则最后剩下的数是多少．
<gadget id="calculator">1 + 100</gadget>
<output>101</output>

<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<gadget id="calculator">101 * 50</gadget>
<output>5_050</output>

<gadget id="calculator">5_050 - 100</gadget>
<output>4_950</output>

<result>4_950</result>