import collections

n = int(input())
num = [ int(v) for v in input().split() ]

moveleft_que, moveright_que = collections.deque([]), collections.deque([])
l, r = 0, 0
ans = 0
for i, v in enumerate(num):
    if v != 1:
        if v == 0:
            if l == 0:
                moveright_que.append(i)
                r += 1
            else:
                p = moveleft_que.popleft()
                l -= 1
                ans += abs(i-p)
        else:
            for _ in range(v-1):
                if r == 0:
                    moveleft_que.append(i)
                    l += 1
                else:
                    p = moveright_que.popleft()
                    r -= 1
                    ans += abs(i-p)

print(ans)