The People's Liberation Army marched 28 kilometers on the first day, 31 kilometers on the second day, 18 kilometers in the morning and 16 kilometers in the afternoon on the third day, how many kilometers per day on average?
解放军行军，第一天行28千米，第二天行31千米，第三天上午行18千米，下午行16千米，平均每天行多少千米？
<gadget id="calculator">28 + 31 + 18 + 16</gadget>
<output>93</output>

<gadget id="calculator">93 / 3</gadget>
<output>31</output>

<result>31</result>