N = int(input())
A = list(map(int, input().split()))
sumA = sum(A)
SW = N
SH = max(A)

rowcnt = 1
cum = 1
row = 0
while cum <= sumA:
    row += 1
    rowcnt += 2
    cum += rowcnt

H = max(max(A), row)
W = max(N, H * 2 - 1)
#print(row,H, W)
S = []

for i in range(H):
    row = []
    for j in range(W):
        if j < N:
            if A[j] > i:
                row.append("#")
            else:
                row.append(".")
        else:
            row.append(".")
    S.append(row)


#print(*S, sep = "\n")
#print("====")

lines = H
ans = 99999
while lines > 0:
    T = []
    blocks = lines * 2 - 1
    right = W - blocks
    left = 0
    for i in range(H):
        if blocks > 0:
            row = ["."] * left + ["#"] * blocks + ["."] * right
        else:
            row = ["."] * W
        T.append(row)
        right += 1
        left += 1
        if blocks > 1:
            blocks -= 2
        else:
            blocks = 0
    

    moveout = 0
    movein = 0
    for i in range(H):
        for j in range(W):
            if S[i][j] == "#" and T[i][j] == ".":
                moveout += 1
            if T[i][j] == "#" and S[i][j] == ".":
                movein += 1

    #print(*T, sep = "\n")
    #print(movein, moveout)
    
    if movein <= moveout:
        ans = min(moveout, ans)
    
    #print("---")
    

    lines -= 1

print(ans)