A circle on a plane can divide the plane into 2 parts; 2 circles can divide the plane into 4 parts at most. Now there are 7 circles, how many parts can the plane be divided into at most?
平面上有一个圆，能把平面分成2部分；2个圆最多能把平面分成4部分．现在有7个圆，最多能把平面分成多少部分．
<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">49 - 7</gadget>
<output>42</output>

<gadget id="calculator">42 + 2</gadget>
<output>44</output>

<result>44</result>