#include <fstream>
#include <vector>
#define NMAX 100001

using namespace std;
ifstream f("darb.in");
ofstream g("darb.out");

vector <int> G[NMAX];
int N,dist[NMAX],best;
bool viz[NMAX];

void dp(int nod)
{
    int max1=0,max2=0,i,frunza=1;

    viz[nod]=1;
    for(i=0;i<G[nod].size();i++)
    {
        if(!viz[G[nod][i]])
        {
            dp(G[nod][i]);
            frunza=0;
            if(dist[G[nod][i]]>max1) {max2=max1; max1=dist[G[nod][i]];}
            else if(dist[G[nod][i]]>max2) max2=dist[G[nod][i]];

        }
    }

    dist[nod]=max1+1;
    if(max1+max2+1>best) best=max1+max2+1;

}

int main()
{
    f>>N;
    int M,i,x,y;

    M=N-1;
    while(M--)
    {
        f>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }

    dp(1);
    g<<best;
}