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<div>
刘海涛x<span class="span-sub">x</span><sub>sub</sub>
</div>
<div>
  刘海涛x<span class="span-super">x</span><sup>sup</sup>
</div>

div {
  margin-bottom: 10px;
}

.span-sub {
  vertical-align: sub;
}
.span-super {
  vertical-align: super;
}