from heapq import *
N = int(input())
B = list(map(int,input().split()))
zero = []
stock = []
count = 0
for i in range(N):
    if B[i] == 0:
        heappush(zero,i)
    elif B[i] == 1:
        pass
    else:
        heappush(stock,(i,B[i]))
while zero != [] and stock != []:
    z = heappop(zero)
    s,i = heappop(stock)
    if i > 1:
        heappush(stock,(s,i-1))
    else:
        s,i = heappop(stock)
        heappush(stock,(s,i-1))
    count += abs(z-s)
print(count)