Fill in the same number in each box of the formula 1□□+1□□+1□□+1□□=□□4 to make the equation true. What is the number filled in?
在算式1□□+1□□+1□□+1□□=□□4的每个方框内填入同一个数字，使得等式成立．所填的数字是多少？
<gadget id="calculator">100 * 4</gadget>
<output>400</output>

<gadget id="calculator">400 - 4</gadget>
<output>396</output>

<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">10 - 40 - 4</gadget>
<output>-34</output>

<gadget id="calculator">100 + (-34)</gadget>
<output>66</output>

<gadget id="calculator">396 / 66</gadget>
<output>6</output>

<result>6</result>