[Baekjoon] 1780, 4779, 1074, 2447 (Divide and Conquer)
1780
10872 https://www.acmicpc.net/problem/10872
https://www.acmicpc.net/problem/9020
https://www.acmicpc.net/problem/2697
https://www.acmicpc.net/problem/2023
https://www.acmicpc.net/problem/13908
https://www.acmicpc.net/problem/1263
https://www.acmicpc.net/problem/25287