N = int(input())
A = list(map(int,input().split()))
B = A[:]
for i in range(1,N):
    B[i] += B[i-1]
suma = sum(A)
x = int(suma ** 0.5)
y = 2 * x - 1
A = A + [0] * y
NA = len(A)
ans = 100 * 100
C = list(range(1,x+1)) + list(reversed(range(1,x))) + [0] * N

for i in range(NA - y + 1):
    tmp = 0
    for j in range(NA):
        tmp += max(0,A[j] - C[j - i])
    ans = min(ans,tmp)
print(ans)