A total of 31 beads of different prices are strung on a rope, and the middle one is the most expensive. Counting from one end, the latter bead is 3 yuan more expensive than the previous one. Until it reaches the middle one; if it is counted from the other end, the latter bead is 4 yuan more expensive than the previous one, until it reaches the middle one. The total value of this string of beads is 2260 yuan, so how much is the middle bead worth?
在一根绳子上串了价格不同的一些珠子共31个，其中正中间那一个最贵，从某一端算起，后一个珠子比前一个贵3元．直至到中间那个为止；若从另一端算起，后一个珠子比前一个贵4元，直至到中间那个为止．这串珠子总价值为2260元，那么中间的那一颗珠子价值多少元．
<gadget id="calculator">2_260 + 840</gadget>
<output>3_100</output>

<gadget id="calculator">3_100 / 31</gadget>
<output>100</output>

<result>100</result>