N = int(input())
B = list(map(int, input().split()))

C = [0 for _ in range(N)]

k = 0

for i in range(N):
    for j in range(B[i]):
        C[k] = i
        k += 1

res = 0

for i in range(N):
    res += abs(C[i] - i)

print(res)