from collections import deque
N=int(input())
P=list(map(int,input().split()))
G=[[]for _ in range(N+1)]
S=[1 for _ in range(N+1)]
for i,p in enumerate(P,1):
    G[i].append(p)
    S[p]=0
ans=0
for i in range(1,N+1):
    if S[i]==0:continue
    Q=deque([([i],1)])
    while Q:
        s,cnt=Q.popleft()
        if cnt==3:
            if len(set(s))==3:ans+=1
            continue
        for nxt in G[s[-1]]:
            if nxt==0:continue
            Q.append((s+[nxt],cnt+1))
print(ans)