What is the single digit of the result obtained by 1*1+2*2+3*3+…+1997*1997?
1*1+2*2+3*3+…+1997*1997所得结果的个位数字是多少．
<gadget id="calculator">4 + 1 + 0</gadget>
<output>5</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>