#include <bits/stdc++.h>

using namespace std;

#define int int64_t

vector<vector<int>> g;
vector<int> depth;
vector<int> up;
vector<bool> used;
vector<pair<int, int>> ans;

void dfs(int v, int p) {
    used[v] = true;
    up[v] = depth[v];
    for (int to: g[v]) {
        if (to == p) {
            continue;
        }
        if (used[to]) {
            up[v] = min(up[v], depth[to]);
            continue;
        }
        depth[to] = depth[v] + 1;
        dfs(to, v);
        up[v] = min(up[v], up[to]);
        if (up[to] == depth[to]) {
            ans.push_back({v, to});
        }
    }
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    int n, m;
    cin >> n >> m;
    g.resize(n);
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        a--; b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    used.assign(n, false);
    depth.resize(n);
    up.resize(n);
    for (int i = 0; i < n; i++) {
        if (!used[i]) {
            dfs(i, -1);
        }
    }
    cout << ans.size() << '\n';
    for (int i = 0; i < ans.size(); i++) {
        cout << ans[i].first + 1 << ' ' << ans[i].second + 1 << '\n';
    }
}