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

balls_index = []
vacant_index = []
for i in range(N):
    b = B[i]
    if b == 0:
        vacant_index.append(i)
    
    else:
        for _ in range(b - 1):
            balls_index.append(i)

ans = 0
for x, y in zip(balls_index, vacant_index):
    ans += abs(x - y)
print(ans)