N = int(input())
P = list(map(int, input().split()))

g = [list() for i in range(N)]
for i in range(N):
    if P[i] != 0:
        g[P[i] - 1].append(i)

depth = [-1] * N


def dfs(v, d=0, pre=-1):
    depth[v] = d
    for u in g[v]:
        if u == pre:
            continue
        dfs(u, d + 1, pre=v)


for i in range(N):
    if P[i] == 0:
        dfs(i)

ans = 0
for i in range(N):
    ans += 1 if depth[i] >= 2 else 0
print(ans)