#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

int main() {
    int n, m; cin >> n >> m;

    vector<vector<int>> adj = vector<vector<int>>(n, vector<int>());
    vector<int> num_neighbors(n, 0);

    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        a -= 1;
        b -= 1;
        adj[a].push_back(b);
        adj[b].push_back(a);
        num_neighbors[a]++;
        num_neighbors[b]++;
    }
    int MIS_ct = 0;
    
    for(int i = 0; i < n; i++) {

        vector<bool> i_nbs(n, false);
        for(int j : adj[i])
            i_nbs[j] = true;

        for(int j = i; j < n; j++) {
            int local_MIS_ct = 1 + ((i==j)?0:1);
            if(i_nbs[j])
                continue;

            vector<bool> out(n, false);

            out[i] = true;
            out[j] = true;
            for(int k : adj[i]) {
                out[k] = true;
                for(int nbnb : adj[k])
                    num_neighbors[nbnb]--;
            }
            for(int k : adj[j]){
                out[k] = true;
                for(int nbnb : adj[k])
                    num_neighbors[nbnb]--;
            }

            while(true) {
                int least_nbs = 10000;
                int best_vertex = -1;
                for(int i = 0; i < n; i++) {
                    if(!out[i] && num_neighbors[i] < least_nbs) {
                        least_nbs = num_neighbors[i];
                        best_vertex = i;
                    }
                }
                if(best_vertex == -1)
                    break;
                out[best_vertex] = true;
                for(int nb: adj[best_vertex]) {
                    out[nb] = true;
                    for(int nbnb : adj[nb])
                        num_neighbors[nbnb]--;
                }
                local_MIS_ct++;
            }
            MIS_ct = max(MIS_ct, local_MIS_ct);
        }
    }

    cout << MIS_ct << endl;

    return 0;
}