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F. Economic Difficulties An electrical grid in Berland palaces consists of 2 grids: main and reserve. Wires in palaces are made of expensive material, 阅读全文
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E. Editor The development of a text editor is a hard problem. You need to implement an extra module for brackets coloring in text. Your editor consist 阅读全文
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D. Secret Passwords One unknown hacker wants to get the admin's password of AtForces testing system, to get problems from the next contest. To achieve 阅读全文
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C. Everyone is a Winner! On the well known testing system MathForces, a draw of n rating units is arranged. The rating will be distributed according t 阅读全文
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B. PIN Codes A PIN code is a string that consists of exactly 4 digits. Examples of possible PIN codes: 7013, 0000 and 0990. Please note that the PIN c 阅读全文
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A. Sweet Problem the first pile contains only red candies and there are r candies in it, the second pile contains only green candies and there are g c 阅读全文