Take two different numbers arbitrarily from 1 to 100 and add them together. How many different methods are there for the sum to be an even number?
在1～100中任意取出两个不同的数相加，其和是偶数的共有多少种不同的取法？
<gadget id="calculator">49 / 2</gadget>
<output>49/2 = around 24.5</output>

<gadget id="calculator">50 * (49/2)</gadget>
<output>1_225</output>

<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">51 * 25</gadget>
<output>1_275</output>

<gadget id="calculator">1_225 + 1_275</gadget>
<output>2_500</output>

<result>2_500</result>