#include <fstream>
#include <algorithm>
#include <vector>
using namespace std;
int n,level[100001],mx,mx2,sol;
vector<int> g[100001],l;
int dfs(int nod,int tt)
{
	int ml=level[nod]=level[tt]+1;
	for(size_t i=0;i<g[nod].size();++i)
	{
		int vecin=g[nod][i];
		if(vecin==tt)
			continue;
		ml=max(ml,dfs(vecin,nod));
	}
	return ml;
}
bool cmp(int a,int b)
{
	return a>b;
}
ifstream fin("darb.in");
ofstream fout("darb.out");
int main()
{
	int x,y;
	fin>>n;
	for(int i=1;i<n;++i)
	{
		fin>>x>>y;
		g[x].push_back(y);
		g[y].push_back(x);
	}
	for(size_t i=0;i<g[1].size();++i)
		l.push_back(dfs(g[1][i],1));
	if(l.size()==1)
	{
		fout<<l[0]+1<<"\n";
		return 0;
	}
	nth_element(l.begin(),l.begin()+1,l.end(),cmp);
	fout<<l[0]+l[1]+1<<"\n";
	return 0;
}