#include<bits/stdc++.h>
using namespace std;
ifstream F("darb.in");
ofstream G("darb.out");
vector<int> v[100001];
bitset<100001> c,u;
int d[100001],m,r,i,j;
void A(int i)
{
    if(c[i]=1,d[i]>m)
        m=d[i],r=i;
    for(auto j:v[i])
        if(!c[j])
            d[j]=d[i]+1,A(j);
}
int main()
{
    for(F>>i;F>>i>>j;v[i].push_back(j),v[j].push_back(i));
    return A(1),memset(d,0,sizeof d),c=u,d[r]=1,A(r),G<<m,0;
}