The user will give a CNF in dimacs format.
设备价格下降，是这门生意能够成立的前提。租金区间从早期的“几万一天”回落到几千元一天，使得更多活动方能够接受成本。这种价格带变化，为市场规模打开了空间。
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There is a plan to prevent such a strike—the Space Surveillance Network, a bevy of sensors that the military uses to track space debris. NASA monitors what’s unofficially known as the “pizza box,” a sort of no-fly zone around the ISS. When pieces of debris are predicted to enter the box—if there’s at least a 1 in 100,000 chance of collision—mission controllers order avoidance maneuvers, firing thrusters that move the ISS and dodge the trash. The technique has been used dozens of times since the first ISS module launched in 1998. But the system only tracks about 45,000 larger pieces, and all sensors have noise. Plus, risk thresholds can miss stuff, sometimes badly. In 2025, Chinese astronauts were briefly stranded at their station after debris hit their return vehicle.
Amazon’s gift card is a physical one that ships with the phone; Best Buy’s is a digital gift card that will be sent to your email after your preorder is fulfilled. At Amazon, instead of the gift card, you also have the option of choosing a free pair of Pixel Buds 2a when you preorder. They are our favorite earbuds, but you probably don’t need them if you already have decent headphones.