#include<bits/stdc++.h>
using namespace std;
int n,tot,minn=2140000000,fa[200005],deg[200005],vis[200005];

void Delete_Degree(int x)
{
	if(!deg[x])vis[x]=1,--deg[fa[x]],Delete_Degree(fa[x]);
	return;
}

void search(int x)
{
	++tot;
	if(vis[x])
	{
		minn=min(minn,tot);
		return;
	}
	else vis[x]=1,search(fa[x]);
}

int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;++i)
	scanf("%d",&fa[i]),++deg[fa[i]];
	for(int i=1;i<=n;++i)
		Delete_Degree(i);
	for(int i=1;i<=n;++i)
		if(!vis[i])
			search(i),tot=0;
	printf("%d",minn-1);
	return 0;
}