#include <fstream>
#include <vector>

using namespace std;
ifstream cin("darb.in");
ofstream cout("darb.out");
vector<int>v[100005];
int dfs(int nd,int lst)
{
    int ad=1,mx1=0;
    for(auto i:v[nd])
    {
        if(i!=lst)
            mx1=max(mx1,dfs(i,nd));
    }
    return ad+mx1;
}
int main()
{
    int n,a,b;
    cin>>n;
    for(int i=1;i<n;i++)
    {
        cin>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    int mx1=0,mx2=0,nd=1,lst=1;
    for(auto i:v[nd])
    {
        if(i!=lst)
        {
            int nr=dfs(i,nd);
            if(nr>mx1)
            {
                mx2=mx1;
                mx1=nr;
            }
            else if(nr>mx2)
                mx2=nr;
        }
    }
    cout<<mx1+mx2+1;
    return 0;
}