BOJ - 17392 - 우울한 방학

import sys

def cal(N):
    sad = 1
    ret = 0

    while sad <= N:
        ret += sad * sad
        sad += 1
    return ret

def solution():
    N, M = map(int, sys.stdin.readline().split())
    arr = list(map(int, sys.stdin.readline().split()))

    sadTotal = M - N - sum(arr)
    total = sadTotal // (N + 1)
    div = sadTotal % (N + 1)

    print(
        cal(total) * (N + 1 - div) + cal(total + 1) * div
    )

solution()

https://www.acmicpc.net/problem/17392