_ = int(input())
B = map(int, input().split())
P = []
Z = []
ans = 0
for i, n in enumerate(B):
    if n == 0:
        Z.append(i)
    elif n > 1:
        P.extend([i] * (n-1))
for z, p in zip(Z, P):
    ans += abs(z - p)
print(ans)