#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin >> n;
    int m;
    cin >> m;
    deque <int> v [n];
    for (int i = 0; i < m; i++)
    {
        int x, y;
        cin >> x >> y;
        v [--x].push_back(--y);
        v [y].push_back(x);
    }
    int ans = 0;
    bool x = 0;
    while (!x)
    {
        bool visited [n] = {};
        x = 1;
        for (int i = 0; i < n; i++)
        {
            if (v [i].size() == 1 && !visited [i])
            {
                v [v [i] [0]].erase(find(v [v [i] [0]].begin(), v [v [i] [0]].end(), i));
                visited [v [i] [0]] = 1;
                visited [i] = 1;
                v [i].pop_back();
                x = 0;
            }
        }
        if (!x)
            ans++;
    }
    cout << ans;
}