3*4+4*5+5*6+...+19*20+20*21.
3*4+4*5+5*6+…+19*20+20*21．
<gadget id="calculator">210 - 8</gadget>
<output>202</output>

<gadget id="calculator">2_870 + 202</gadget>
<output>3_072</output>

<result>3_072</result>