#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <queue>
#include <sstream>
#include <iterator>
#include <iomanip>
#include <cstdio>
#include <climits>
#include <float.h>
#include <cmath>

#define forn(i, n) for (int i = 0; i < int(n); i++)
#define forn1(i, n) for (int i = 1; i < int(n); i++)
#define forr(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define forit(it, a) for (auto it = (a).begin(); it != (a).end(); it++)
#define all(a) (a).begin(), (a).end()
#define mp make_pair
#define pb push_back
#define fir first
#define sec second

using namespace std;

typedef long long ll;
typedef pair<int, int> pt;

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};

vector <vector <int>> graph_rev;
vector <bool> used;

int main(){
    ios_base::sync_with_stdio(false);
    int n, m;
	cin >> n >> m;
	vector <set<int>> edges(n);
	forn(i, m)
	{
		int x, y;
		cin >> x >> y;
		x--; y--;
		edges[x].insert(y);
		edges[y].insert(x);
	}
	vector <bool> mark(n);
	int cnt = 0;
	while (true)
	{
		used = vector <bool> (n);
		bool flag = false;
		forn(i, n)
		{
			if (!used[i] && !mark[i] && edges[i].size() == 1)
			{
				forit(it, edges[i])
				{
					int to = *it;
					used[to] = true;
					edges[to].erase(i);
				}
				edges[i].clear();
				used[i] = true;
				mark[i] = true;
				flag = true;
			}
		}
		if (!flag)
			break;
		else
			cnt++;
	}
	cout << cnt << endl;
    return 0;
}