#include <iostream>
#include <cassert>
#include <vector>
using namespace std;

template <typename T, T (*op)(T, T)>
struct union_find
{
    int n;
    std::vector<int> par;
    std::vector<int> sz;
    std::vector<T> dat;
    int num_of_components;

    union_find(int n) : n(n)
    {
        par.resize(n);
        sz.resize(n);
        dat.resize(n);
        for (int i = 0; i < n; i++)
        {
            par[i] = i;
            sz[i] = 1;
        }
        num_of_components = n;
    }

    union_find(std::vector<T> &dat) : dat(dat)
    {
        union_find(dat.size());
    }

    int find(int i)
    {
        assert(0 <= i && i < n);
        return (i == par[i]) ? i : par[i] = find(par[i]);
    }

    bool same(int i, int j)
    {
        assert(0 <= i && i < n);
        assert(0 <= j && j < n);
        return find(i) == find(j);
    }

    void unite(int i, int j)
    {
        assert(0 <= i && i < n);
        assert(0 <= j && j < n);
        i = find(i), j = find(j);
        if (sz[i] < sz[j])
        {
            std::swap(i, j);
        }
        dat[i] = op(dat[i], dat[j]);
        if (i == j)
        {
            return;
        }
        par[j] = i;
        sz[i] += sz[j];
        num_of_components--;
    }

    int size()
    {
        return n;
    }

    int size(int i)
    {
        assert(0 <= i && i < n);
        return sz[find(i)];
    }

    T weight(int i)
    {
        assert(0 <= i && i < n);
        return dat[find(i)];
    }

    int count()
    {
        return num_of_components;
    }

    bool is_root(int i)
    {
        assert(0 <= i && i < n);
        return i == find(i);
    }

    int operator[](int i)
    {
        return find(i);
    }
};

int op(int a, int b)
{
    return max(a, b) + 1;
}

int main()
{
    int n, m;
    cin >> n >> m;
    union_find<int, op> uf(n);
    int u[200005], v[200005];
    for (int i = 0; i < m; i++)
    {
        cin >> u[i] >> v[i];
        u[i]--;
        v[i]--;
    }
    for (int i = m - 1; i >= 0; i--)
    {
        uf.unite(u[i], v[i]);
    }
    int ans = 0;
    for (int x = 0; x < n; x++)
    {
        ans = max(ans, uf.weight(x));
    }
    cout << ans << endl;
}