If the letter of the English word he11o is wrongly written, how many possible mistakes can occur?
把英语单词he11o的字母写错了，则可能出现的错误共有多少种．
<gadget id="calculator">5 * 4 * 3 * 2 * 1</gadget>
<output>120</output>

<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<gadget id="calculator">60 - 1</gadget>
<output>59</output>

<result>59</result>