求助

#include<bits/stdc++.h>
using namespace std;
int a[200005];
bool vis[200005] = {0};
int n,ans = 0;
int main(){
	scanf("%d",&n);
	for(int i = 1;i <= n;i++){
		int t;
		scanf("%d",&t);
		a[i] = t;
	}
	int now = 1;
	while(1){
		if(vis[now] == 1) break;
		vis[now] = 1;
		now = a[now];
	}
	int now1 = now;
	for(int i = 1;i <= n;i++){
		if(i > 1 && now1 == now) break;
		ans++;
		now1 = a[now1];
	}
	printf("%d",ans);
	return 0;
}