A certain grain store has several kilograms of grain in stock at the beginning of a certain month, sells half of the stock in the first week of the month, does not sell the grain in the second week, but buys 450 kg of grain, and sells the existing grain in the third week Half of the grain and 50 kilograms, did not sell grain in the fourth week, but bought (2/3) of the existing (at that time) grain as inventory. At the end of the month, it was found that the grain store still had 1,000 kilograms of grain. Ask the grain owner How many kilograms of original grain at the beginning of the month?
某粮店某月初存有粮食若干千克，该月的第一个星期卖出存粮的一半，第二个星期没有卖出粮食，但买进450千克的粮食，第三个星期又卖出现有粮食的一半又50千克，第四个星期没有卖出粮食，但又买进现有(当时)粮食的(2/3)作为库存，月末盘存时发现粮店还有1000千克的粮食，问粮食本月初原有粮食多少千克？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 + (2/3)</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">1_000 / (5/3)</gadget>
<output>600</output>

<gadget id="calculator">600 + 50</gadget>
<output>650</output>

<gadget id="calculator">650 * 2</gadget>
<output>1_300</output>

<gadget id="calculator">1_300 - 450</gadget>
<output>850</output>

<gadget id="calculator">850 * 2</gadget>
<output>1_700</output>

<result>1_700</result>