There are 50 red flags planted on one side of the road. If a yellow flag is placed between every two red flags, how many yellow flags will be planted in total?
马路的一边插了50面红旗，如果每两面红旗中间插一面黄旗，一共要插多少面黄旗．
<gadget id="calculator">50 - 1</gadget>
<output>49</output>

<result>49</result>