What is the sum of all natural numbers whose quotients are equal to the remainders obtained when divided by 15?
所有除以15所得的商数等于所得余数的自然数之和等于多少．
<gadget id="calculator">14 * 15</gadget>
<output>210</output>

<gadget id="calculator">210 + 14</gadget>
<output>224</output>

<gadget id="calculator">1 * 15</gadget>
<output>15</output>

<gadget id="calculator">15 + 1</gadget>
<output>16</output>

<gadget id="calculator">224 + 16</gadget>
<output>240</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">240 * 7</gadget>
<output>1_680</output>

<result>1_680</result>