from collections import deque
N = int(input())
B = [int(b) for b in input().split()]

ans = 0
q = deque()
for i in range(N):
    if B[i] == 0:
        q.append(i)
for i in range(N):
    while B[i] > 1:
        B[i] -= 1
        t = q.popleft()
        ans += abs(t-i)

print(ans)