#include <bits/stdc++.h>
#define NMAX 100005
#define cin fin
#define cout fout

using namespace std;
ifstream fin("darb.in");
ofstream fout("darb.out");

int n, d[NMAX], t[NMAX], r;
vector<int> v[NMAX];

void read();
void DFS(int nod);
int main()
{
    read();

    //aflam radacina
    for(int i=1; i<=n; ++i)
        if(t[i]==0)
            r=i;

    d[r]=1;
    DFS(r);

    int max1, max2;
    max1=max2=0;

    for(int i=1; i<=n; ++i)
    {
        if(d[i]>max1)
        {
            max2=max1;
            max1=d[i];
        }
        else if(d[i]>max2)
            max2=d[i];
    }

    cout<<max1+max2-1<<'\n';
    return 0;
}
void DFS(int nod)
{
    for(int i=0; i<v[nod].size(); ++i)
    {
        int a=v[nod][i];
        d[a]=d[nod]+1;
        DFS(a);
    }
}
void read()
{
    cin>>n;
    for(int i=1; i<n; ++i)
    {
        int x, y;
        cin>>x>>y;
        v[x].push_back(y);
        t[y]=x;
    }
}