There are 2003 numbers on the blackboard, two numbers are erased arbitrarily each time, and another one is written. After how many times, there is only one number left on the blackboard.
黑板上有2003个数，每次任意擦掉两个数，再写上一个．经过多少次后，黑板上只剩一个数．
<gadget id="calculator">2_003 - 2</gadget>
<output>2_001</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">2_001 / 1</gadget>
<output>2_001</output>

<gadget id="calculator">2_001 + 1</gadget>
<output>2_002</output>

<result>2_002</result>