#define LOCAL
#include <bits/stdc++.h>
using namespace std;
#pragma region Macros
typedef long long ll;
typedef __int128_t i128;
typedef unsigned int uint;
typedef unsigned long long ull;
#define ALL(x) (x).begin(), (x).end()

template <typename T> istream& operator>>(istream& is, vector<T>& v) {
    for (T& x : v) is >> x;
    return is;
}
template <typename T> ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0; i < (int)v.size(); i++) {
        os << v[i] << (i + 1 == (int)v.size() ? "" : " ");
    }
    return os;
}
template <typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template <typename T, typename U, typename V> ostream& operator<<(ostream& os, const tuple<T, U, V>& t) {
    os << '(' << get<0>(t) << ',' << get<1>(t) << ',' << get<2>(t) << ')';
    return os;
}
template <typename T, typename U, typename V, typename W> ostream& operator<<(ostream& os, const tuple<T, U, V, W>& t) {
    os << '(' << get<0>(t) << ',' << get<1>(t) << ',' << get<2>(t) << ',' << get<3>(t) << ')';
    return os;
}
template <typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& m) {
    os << '{';
    for (auto itr = m.begin(); itr != m.end();) {
        os << '(' << itr->first << ',' << itr->second << ')';
        if (++itr != m.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T, typename U> ostream& operator<<(ostream& os, const unordered_map<T, U>& m) {
    os << '{';
    for (auto itr = m.begin(); itr != m.end();) {
        os << '(' << itr->first << ',' << itr->second << ')';
        if (++itr != m.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const set<T>& s) {
    os << '{';
    for (auto itr = s.begin(); itr != s.end();) {
        os << *itr;
        if (++itr != s.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const multiset<T>& s) {
    os << '{';
    for (auto itr = s.begin(); itr != s.end();) {
        os << *itr;
        if (++itr != s.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const unordered_set<T>& s) {
    os << '{';
    for (auto itr = s.begin(); itr != s.end();) {
        os << *itr;
        if (++itr != s.end()) os << ',';
    }
    os << '}';
    return os;
}
template <typename T> ostream& operator<<(ostream& os, const deque<T>& v) {
    for (int i = 0; i < (int)v.size(); i++) {
        os << v[i] << (i + 1 == (int)v.size() ? "" : " ");
    }
    return os;
}

void debug_out() { cerr << '\n'; }
template <class Head, class... Tail> void debug_out(Head&& head, Tail&&... tail) {
    cerr << head;
    if (sizeof...(Tail) > 0) cerr << ", ";
    debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                                   \
    cerr << " ";                                                                     \
    cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << '\n'; \
    cerr << " ";                                                                     \
    debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1& a, T2 b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T1, class T2> inline bool chmax(T1& a, T2 b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
#pragma endregion

/**
 * @brief UnionFind
 * @docs docs/datastructure/UnionFind.md
 */
struct UnionFind {
    int num;
    vector<int> par, rank;
    UnionFind(int n) : num(n), par(n), rank(n, 1) { iota(par.begin(), par.end(), 0); }
    int root(int x) { return (par[x] == x ? x : par[x] = root(par[x])); }
    bool merge(int x, int y) {
        x = root(x);
        y = root(y);
        if (x == y) return false;
        if (rank[x] < rank[y]) swap(x, y);
        par[y] = x;
        rank[x] += rank[y];
        num--;
        return true;
    }
    bool same(int x, int y) { return root(x) == root(y); }
    int size(int x) { return rank[root(x)]; }
    int count() { return num; }
    int operator[](int x) { return root(x); }
};

/**
 * @brief Cycle Detection
 * @docs docs/graph/CycleDetection.md
 */
template <bool directed> struct CycleDetection {
    vector<vector<int>> G;
    vector<int> seen, finished;
    stack<int> hist;
    int pos;
    CycleDetection(int n) : G(n), seen(n, 0), finished(n, 0), pos(-1) {}
    void add_edge(int u, int v) { G[u].emplace_back(v); }
    void dfs(int v, int p) {
        seen[v] = 1;
        hist.emplace(v);
        for (int u : G[v]) {
            if (!directed && u == p) continue;
            if (finished[u]) continue;
            if (seen[u] && !finished[u]) {
                pos = u;
                return;
            }
            dfs(u, v);
            if (~pos) return;
        }
        finished[v] = 1;
        hist.pop();
    }
    vector<int> build() {
        for (int v = 0; v < (int)G.size(); v++) {
            if (!seen[v]) dfs(v, -1);
            if (~pos) break;
        }
        vector<int> res;
        while (!hist.empty()) {
            int t = hist.top();
            hist.pop();
            res.emplace_back(t);
            if (t == pos) break;
        }
        return res;
    }
};

/**
 * @brief Topological Sort
 * @docs docs/graph/TopologicalSort.md
 */
struct TopologicalSort {
    vector<vector<int>> G;
    vector<int> seen, order;
    TopologicalSort(int n) : G(n), seen(n) {}
    void add_edge(int u, int v) { G[u].emplace_back(v); }
    void dfs(int v) {
        seen[v] = 1;
        for (int u : G[v]) {
            if (!seen[u]) dfs(u);
        }
        order.emplace_back(v);
    }
    vector<int> build() {
        for (int i = 0; i < (int)G.size(); i++) {
            if (!seen[i]) dfs(i);
        }
        reverse(order.begin(), order.end());
        return order;
    }
    int operator[](int i) { return order[i]; }
};

/**
 * @brief compress
 */
template <typename T> map<T, int> compress(vector<T>& v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    map<T, int> res;
    for (int i = 0; i < v.size(); i++) res[v[i]] = i;
    return res;
}

const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};
const long long MOD = 1000000007;
// const long long MOD = 998244353;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, M;
    cin >> N >> M;
    vector<int> U(M), V(M);
    UnionFind UF(N);
    for (int i = 0; i < M; i++) {
        cin >> U[i] >> V[i];
        UF.merge(--U[i], --V[i]);
    }

    vector<vector<int>> group(N), es(N);
    for (int i = 0; i < N; i++) group[UF[i]].emplace_back(i);
    for (int i = 0; i < M; i++) es[UF[U[i]]].emplace_back(i);
    vector<pair<int, int>> ans;

    for (int i = 0; i < N; i++) {
        if (group[i].empty()) continue;
        int sz = group[i].size();
        CycleDetection<true> CD(sz);
        TopologicalSort TS(sz);
        map<int, int> mp = compress(group[i]);
        for (int& e : es[i]) {
            CD.add_edge(mp[U[e]], mp[V[e]]);
            TS.add_edge(mp[U[e]], mp[V[e]]);
        }
        if (!CD.build().empty()) {
            for (int j = 0; j < sz; j++) {
                ans.emplace_back(group[i][j], group[i][(j + 1) % sz]);
            }
        } else {
            TS.build();
            for (int j = 0; j < sz - 1; j++) ans.emplace_back(group[i][TS[j]], group[i][TS[j + 1]]);
        }
    }

    cout << ans.size() << '\n';
    for (auto& p : ans) cout << p.first + 1 << ' ' << p.second + 1 << '\n';
    return 0;
}