###################
###蟻本を読もう!###
###################


n = input()
a = map(int, raw_input().split())


k = 1
while((k+1)**2 <= sum(a)):k+=1

a += [0] * (k*3)
extra = sum(a) - k*k
res = 0

for x in xrange(len(a)):
	if x < k:
		res += abs(a[x] - (x+1))
	elif x < k * 2-1:
		res += abs(a[x] - (k*2-x))
	else: res += a[x]

print (res + extra) / 2