Helium is used to pressurize tanks and help push fuel into the engines. Without proper helium flow, the rocket cannot safely fly. Because the upper stage is hard to reach at the launchpad, NASA rolled the stacked rocket back into the Vehicle Assembly Building, the sky-scraping hangar where it was originally put together.
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bingbangboom-lab
* 获取数字的第digit位（从右往左，0表示个位）