CodeForces补题计划

由于做不动省选题，学不动省选知识点，于是来刷CodeForces了

• Codeforces Round #668 (Div. 1) (A/B/C)
• Codeforces Round #673 (Div. 1) (A/B/C/D)
• Codeforces Raif Round 1 (Div. 1 + Div. 2) (A/B/C/E)
• Codeforces Round #679 (Div. 1, based on Technocup 2021 Elimination Round 1) (A/B/C)
• Codeforces Round #680 (Div. 1, based on Moscow Team Olympiad) (A/B)
• Codeforces Round #681 (Div. 1, based on VK Cup 2019-2020 - Final) (A)
• Codeforces Round #683 (Div. 1, by Meet IT) (A/B/C)
• Codeforces Round #684 (Div. 1)(A1/A2/C)