N = int(input())
A = list(map(int,input().split()))
A.insert(0,0)
G = {i:[] for i in range(1,N+1)}
for i in range(1,N):
    a = A[i]+1
    G[a].append(i+1)
k = 0
while 2**k<N:
    k += 1
K = 2**k
B = [0 for _ in range(K+1)]
def update(i,x):
    j = i
    while j<=K:
        B[j] += x
        j += j&(-j)
def csum(i):
    j = i
    tot = 0
    while j>0:
        tot += B[j]
        j -= j&(-j)
    return tot
cnt = 0
def dfs(i):
    global cnt
    cnt += csum(i)
    update(i,1)
    for j in G[i]:
        dfs(j)
        update(j,-1)
dfs(1)
print(cnt)