#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define f first
#define s second
#define pf push_front
#define pb push_back
#define pi pair<int,int>
#define vi vector<int>
const int MAX = 2001;
vi g[MAX];
ll ans = 0;
void dfs(int from , int p, ll dis){
if(g[from].size()==1) ans = max(ans,dis);
for(int to : g[from]){
if(to==p)continue;
dfs(to,from,dis+1);
}
}
int travel_plan(int N, int M, int R[][2], int L[], int K, int P[]){
for(int i = 0; i< M; i++){
int a = R[i][0];
int b = R[i][1];
g[a].pb(b);
g[b].pb(a);
}
dfs(0,-1,0);
return ans;
}
