import math

n = int(input())
a = [int(x) for x in input().split()]

brick = sum(a)
height = math.floor(math.sqrt(brick))
width = height * 2 - 1
piramid = [0] * width
for i in range(width // 2):
    piramid[i] = i + 1
    piramid[width - 1 - i] = piramid[i]
piramid[width // 2] = height

res = 0
for i in range(len(a)):
    if i >= len(piramid):
        res += a[i]
        continue
    if a[i] > piramid[i]:
        res += a[i] - piramid[i]

print(res)