#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
using ll = long long;
using pii = pair<int,int>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<typename T> T uid(T x, T y) {return uniform_int_distribution<T>(x,y)(rng);}
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) {os << "["; for (int i = 0; i < v.size(); i++) {if (i) os << ", "; os << v[i];} return os << "]";};
template<typename... Ts> ostream& operator<<(ostream& os, const pair<Ts...>& x) {return os << "(" <<x.first << ", " << x.second << ")";};
template<typename T> void pv(T a, T b, string s = "") {cerr << "["; for (T i = a; i != b; ++i) {if (i != a) cerr << ", "; cerr << *i;} cerr << "] " << s << "\n";}
template<typename T> void pv(const T& t, string s = "") {pv(begin(t), end(t), s);}
template<typename... T> void dbg(T... t) {initializer_list<int>{(cerr << t << " ", 0)...}; cerr << "\n";}
template<typename T, typename U> void chmin(T& t, U u) {if (t > u) t = u;}
template<typename T, typename U> void chmax(T& t, U u) {if (t < u) t = u;}
#define bug(x...) cerr << "[" << #x << "] = ", dbg(x)
#define fi first
#define se second
#define SZ(x) ((int)((x).size()))
const int mx = 5e5+5;
vector<int> adj[mx], cyc;
vector<int> allvis;
vector<pii> ans;
int vis[mx];
bool tr = true;
void dfs(int v, int p) {
    vis[v] = 1;
    allvis.push_back(v);
    for (int a : adj[v]) {
        if (a == p) continue;
        if (vis[a]) {
            tr = false;
            if (SZ(cyc) == 0) {
                cyc.push_back(v);
            }
        }
        else {
            dfs(a,v);
        }
    }
}
void dfs1(int v, int p) {
    int ct = 0;
    for (int a : adj[v]) {
        if (a == p) continue;
        dfs1(a,v);
        ct++;
    }
    if (ct == 0 && p != 0) ans.emplace_back(v,p);
}
int dep[mx], oncyc[mx], vis1[mx];
void dfs2(int v, int p) {
    vis1[v] = 1;
    for (int a : adj[v]) {
        if (a == p) continue;
        if (vis1[a]) {
            oncyc[v] = 1;
            continue;
        }
        dep[a] = dep[v]+1;
        dfs2(a,v);
        oncyc[v] |= oncyc[a];
    }
}
void dfs3(int v, int p) {
    for (int a : adj[v]) {
        if (dep[a] == dep[v]+1) {
            dfs3(a,v);
        }
    }
    if (p != 0 && !oncyc[v] && oncyc[p]) {
        ans.emplace_back(p,v);
    }
}
void solve(istream& cin = std::cin, ostream& cout = std::cout) {
    int n,m;
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int a,b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    for (int i = 1; i <= n; i++) {
        if (!vis[i]) {
            tr = true;
            cyc.clear();
            allvis.clear();
            // check if tree
            dfs(i,0);
            if (tr) {
                // if it is, just mark the leaves
                if (SZ(allvis) == 2) {
                    ans.emplace_back(allvis[0],allvis[1]);
                    ans.emplace_back(allvis[1],allvis[0]);
                    continue;
                }
                int rt = i;
                for (int v : allvis) {
                    if (SZ(adj[v]) > 1) rt = v;
                }
                dfs1(rt,0);
            } else {
                assert(SZ(cyc) == 1);
                int rt = cyc[0];
                dfs2(rt,0);
                dfs3(rt,0);
            }
        }
    }
    sort(ans.begin(),ans.end());
    cout << SZ(ans) << '\n';
    for (auto [a,b] : ans) cout << a << ' ' << b << '\n';
}
signed main() {
    ios::sync_with_stdio(0); cin.tie(0);
    int t = 1;
//    cin >> t;
    for (int q = 1; q <= t; q++) {
        solve();
    }
    return 0;
}