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

ans = 0
for i in range(N):
    if i + 1 == P[i]:
        continue
    for j in range(i + 1, N):
        if i + 1 != P[j]:
            continue
        P[i], P[j] = P[j], P[i]
        ans += 1
        break

print(ans)