#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int dfs(vector<vector<int>>& graph, vector<int>& neighbor, vector<int>& dp, int cur) {
if (dp[cur]) return dp[cur];//이미 계산한 경우예요
int cnt = 1;//나 자신
for (auto& next : graph[cur]) {//탐색해요
if (neighbor[cur] < neighbor[next]) {
cnt = max(1 + dfs(graph, neighbor, dp, next), cnt);
}//이웃이 더 많다면 최댓값을 갱신해요
}
return dp[cur] = cnt;//값을 저장해요
}
int main(void) {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n, m; cin >> n >> m;
vector<vector<int>> graph(n);
vector<int> neighbor(n);
vector<int> dp(n);
for (int edge = 0, i, j; edge < m; edge++) {
cin >> i >> j;
//graph를 갱신해요
graph[i].push_back(j);
graph[j].push_back(i);
//이웃을 증가시켜줘요
neighbor[i]++;
neighbor[j]++;
}
int biggest = 0;//최댓값을 찾아요
for (int i = 0; i < n; i++) {
biggest = max(biggest, dfs(graph, neighbor, dp, i));
}
cout << biggest << '\n';
return 0;
}
