#include <bits/stdc++.h>

using namespace std;

#define int long long
#define rep(i, n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i, n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define miele(v) min_element(v.begin(), v.end())
#define maele(v) max_element(v.begin(), v.end())
#define SUM(v) accumulate(v.begin(), v.end(), 0LL)
#define lb(a, key) lower_bound(a.begin(),a.end(),key)
#define ub(a, key) upper_bound(a.begin(),a.end(),key)
#define COUNT(a, key) count(a.begin(), a.end(), key)
#define BITCOUNT(x) __builtin_popcount(x)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
using P = pair<int, int>;
using WeightedGraph = vector<vector<P>>;
using UnWeightedGraph = vector<vector<int>>;
using Real = long double;
using Point = complex<Real>; //Point and Vector2d is the same!
// p.real() or real(p) -> x軸, p.imag() or imag(p) -> y軸
using Vector2d = complex<Real>;
const int MOD = 1000000007;
const long long INF = 1LL << 60;
const double EPS = 1e-15;
const double PI = 3.14159265358979323846;

template<typename T>
int getIndexOfLowerBound(vector<T> &v, T x) {
    return lower_bound(v.begin(), v.end(), x) - v.begin();
}

template<typename T>
int getIndexOfUpperBound(vector<T> &v, T x) {
    return upper_bound(v.begin(), v.end(), x) - v.begin();
}

template<class T>
inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)

istream &operator>>(istream &is, Point &p) {
    Real a, b;
    is >> a >> b;
    p = Point(a, b);
    return is;
}

template<typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p_var) {
    is >> p_var.first >> p_var.second;
    return is;
}

template<typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}

template<typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    os << pair_var.first << ' ' << pair_var.second;
    return os;
}

template<typename T>
ostream &operator<<(ostream &os, vector<T> &vec) {
    for (int i = 0; i < vec.size(); i++)
        os << vec[i] << ' ';
    return os;
}

template<typename T, typename U>
ostream &operator<<(ostream &os, vector<pair<T, U>> &vec) {
    for (int i = 0; i < vec.size(); i++)
        os << vec[i] << '\n';
    return os;
}

template<typename T>
ostream &operator<<(ostream &os, vector<vector<T>> &df) {
    for (auto &vec : df) os << vec;
    return os;
}

template<typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    repi(itr, map_var) {
        os << *itr << ' ';
        itr++;
        itr--;
    }
    return os;
}

template<typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    repi(itr, set_var) {
        os << *itr << ' ';
        itr++;
        itr--;
    }
    return os;
}

void print() { cout << endl; }

template<class Head, class... Tail>
void print(Head &&head, Tail &&... tail) {
    cout << head;
    if (sizeof...(tail) != 0) cout << " ";
    print(forward<Tail>(tail)...);
}

//#https://ei1333.github.io/luzhiled/snippets/graph/strongly-connected-components.htmlお借りしますorz
template<typename G>
struct StronglyConnectedComponents {
    const G &g;
    UnWeightedGraph gg, rg;
    vector<int> comp, order, used;

    StronglyConnectedComponents(G &g) : g(g), gg(g.size()), rg(g.size()), comp(g.size(), -1), used(g.size()) {
        for (int i = 0; i < g.size(); i++) {
            for (auto e : g[i]) {
                gg[i].emplace_back((int) e);
                rg[(int) e].emplace_back(i);
            }
        }
    }

    int operator[](int k) {
        return comp[k];
    }

    void dfs(int idx) {
        if (used[idx]) return;
        used[idx] = true;
        for (int to : gg[idx]) dfs(to);
        order.push_back(idx);
    }

    void rdfs(int idx, int cnt) {
        if (comp[idx] != -1) return;
        comp[idx] = cnt;
        for (int to : rg[idx]) rdfs(to, cnt);
    }

    void build(UnWeightedGraph &t) {
        for (int i = 0; i < gg.size(); i++) dfs(i);
        reverse(begin(order), end(order));
        int ptr = 0;
        for (int i : order) if (comp[i] == -1) rdfs(i, ptr), ptr++;

        t.resize(ptr);
        for (int i = 0; i < g.size(); i++) {
            for (auto &to : g[i]) {
                int x = comp[i], y = comp[to];
                if (x == y) continue;
                t[x].push_back(y);
            }
        }
    }
};

signed main(void) { cin.tie(0); ios::sync_with_stdio(false);
    int n, m; cin>>n>>m;
    UnWeightedGraph g(n), bidirectional_g(n);

    rep(i, m) {
        int u, v; cin>>u>>v;
        u--, v--;
        g[u].pb(v);
        bidirectional_g[u].pb(v);
        bidirectional_g[v].pb(u);
    }

    StronglyConnectedComponents<UnWeightedGraph> scc(bidirectional_g);
    UnWeightedGraph t;
    scc.build(t);

    UnWeightedGraph newG(n);

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < g[i].size(); ++j) {
            if(scc[g[i][j]] == scc[i]) {
                newG[i].pb(g[i][j]);
            }
        }
    }

    vector<vector<int>> elementList(t.size());
    vector<int> deg(n);
    for (int i = 0; i < n; ++i) {
        elementList[scc[i]].pb(i);
        for (auto to : newG[i]) {
            deg[to]++;
        }
    }

    vector<pair<int, int>> ans;
    vector<int> used(t.size());
    // deg[i] == 0 の iを見つけたらトポロジカルソートをする

    for (int i = 0; i < n; ++i) {
        if(!used[scc[i]]) {
            used[scc[i]] = true;
            queue<int> q;
            stack<int> st;
            for (int j = 0; j < elementList[scc[i]].size(); ++j) {
                if(deg[elementList[scc[i]][j]] == 0) {
                    st.push(elementList[scc[i]][j]);
                    q.push(elementList[scc[i]][j]);
                }
            }

            while(!st.empty()) {
                int now = st.top(); st.pop();

                for (int j = 0; j < newG[now].size(); ++j) {
                    deg[newG[now][j]]--;
                    if(deg[newG[now][j]]==0) {
                        q.push(newG[now][j]);
                        st.push(newG[now][j]);
                    }
                }
            }

            if(q.size() == elementList[scc[i]].size()) {

                int now = q.front(); q.pop();
                while(!q.empty()) {
                    int ne = q.front(); q.pop();
                    ans.pb({now, ne});
                    now = ne;
                }
            } else {

                int now = -1;
                int first = -1;
                int group = scc[i];
                for (int j = 0; j < elementList[group].size(); ++j) {
                    int e = elementList[group][j];
                    if(j == 0) {
                        now = first = e;
                    } else if(j == elementList[group].size() - 1) {
                        ans.pb({now, e});
                        ans.pb({e, first});
                    } else {
                        ans.pb({now, e});
                        now = e;
                    }
                }
            }
        }
    }

    print(ans.size());

    for (int i = 0; i < ans.size(); ++i) {
        print(ans[i].F+1, ans[i].S+1);
    }
}