Take out two different numbers from the 50 numbers of 1, 2, 3, 4, ..., 50, how many different ways are there to make the result of adding the two numbers taken out be a multiple of 3?
在1，2，3，4，…，50这50个数中取出不同的两个数，要使取出的两个数相加的结果是3的倍数，有多少种不同的取法．
<gadget id="calculator">16 * 15</gadget>
<output>240</output>

<gadget id="calculator">240 / 2</gadget>
<output>120</output>

<gadget id="calculator">17 * 17</gadget>
<output>289</output>

<gadget id="calculator">120 + 289</gadget>
<output>409</output>

<result>409</result>