N=int(input())
P=[0]+list(map(int,input().split()))
ans=0
for i,nxt in enumerate(P):
    grp=set([i])
    for _ in range(2):
        grp.add(nxt)
        nxt=P[nxt]
    if len(grp)==3 and 0 not in grp:
        ans+=1
print(ans)