#include "bits/stdc++.h"
#include <random>
#include <chrono>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ALL(x) (x).begin(), (x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define SZ(x) ((lint)(x).size())
#define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;++i)
#define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;--i)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define endk '\n'
using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef long double ld; typedef pair<lint, lint> plint;
struct fast_ios { fast_ios() { cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_;
template<class T> auto add = [](T a, T b) -> T { return a + b; };
template<class T> auto f_max = [](T a, T b) -> T { return max(a, b); };
template<class T> auto f_min = [](T a, T b) -> T { return min(a, b); };
template<class T> using V = vector<T>;
using Vl = V<lint>; using VVl = V<Vl>;
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 != v.size() ? " " : "");
	return os;
}
template< typename T >istream& operator>>(istream& is, vector< T >& v) {
	for (T& in : v) is >> in;
	return is;
}
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
template <class T>
T div_floor(T a, T b) {
	if (b < 0) a *= -1, b *= -1;
	return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
	if (b < 0) a *= -1, b *= -1;
	return a > 0 ? (a - 1) / b + 1 : a / b;
}
template <class F> struct rec {
	F f;
	rec(F&& f_) : f(std::forward<F>(f_)) {}
	template <class... Args> auto operator()(Args &&... args) const {
		return f(*this, std::forward<Args>(args)...);
	}
};
template <typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2>& l, const pair<T1, T2>& r) { return make_pair(l.first + r.first, l.second + r.second); }
template <typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2>& l, const pair<T1, T2>& r) { return make_pair(l.first - r.first, l.second - r.second); }
lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); }
lint digit(lint a) { return (lint)log10(a); }
lint e_dist(plint a, plint b) { return abs(a.first - b.first) * abs(a.first - b.first) + abs(a.second - b.second) * abs(a.second - b.second); }
lint m_dist(plint a, plint b) { return abs(a.first - b.first) + abs(a.second - b.second); }
bool check_overflow(lint a, lint b, lint limit) { if (b == 0) return false; return a > limit / b; } // a * b > c => true
void Worshall_Floyd(VVl& g) { REP(k, SZ(g)) REP(i, SZ(g)) REP(j, SZ(g)) chmin(g[i][j], g[i][k] + g[k][j]); }
const lint MOD1000000007 = 1000000007, MOD998244353 = 998244353, INF = 1e18;
lint dx[8] = { 0, -1, 0, 1, 1, -1, 1, -1 }, dy[8] = { -1, 0, 1, 0, -1, -1, 1, 1 };
bool YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; return flag; } bool yn(bool flag) { cout << (flag ? "Yes" : "No") << endk; return flag; }
struct Edge {
	lint from, to;
	lint cost, color;
	Edge() {

	}
	Edge(lint u, lint v, lint c, lint col) {
		cost = c;
		color = col;
		from = u;
		to = v;
	}
	bool operator<(const Edge& e) const {
		return cost < e.cost;
	}
};
struct WeightedEdge {
	lint to;
	lint cost;
	lint d;
	WeightedEdge(lint v, lint c, lint _d) {
		to = v;
		cost = c;
		d = _d;
	}
	bool operator<(const WeightedEdge& e) const {
		return cost < e.cost;
	}
};
using WeightedGraph = V<V<WeightedEdge>>;
typedef pair<lint, plint> tlint;
typedef pair<plint, plint> qlint;
typedef pair<string, lint> valstr;
typedef pair<ld, lint> pld;
typedef pair<ld, lint> pidx;

template< typename G >
struct StronglyConnectedComponents {
	const G& g;
	VVl 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(VVl& 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);
			}
		}
	}
};


int main() {
	lint N, M;
	cin >> N >> M;
	VVl to(N);
	REP(i, M) {
		lint u, v;
		cin >> u >> v; u--; v--;
		to[u].push_back(v);
	}
	StronglyConnectedComponents<VVl> g(to);
	VVl res;
	g.build(res);
	VVl _to(N);
	REP(i, N) _to[g.comp[i]].push_back(i);
	V<plint> ans;
	lint prv = -1;
	REP(i, SZ(_to)) {
		if (SZ(_to[i]) == 0) continue;
		if (prv != -1) {
			ans.push_back({ prv + 1, _to[i][0] + 1 });
		}
		prv = _to[i][0];
	}
	REP(i, SZ(_to)) {
		if (SZ(_to[i]) == 0) continue;
		if (SZ(_to[i]) == 1) continue;
		REP(j, SZ(_to[i])) {
			ans.push_back({ _to[i][j] + 1, _to[i][(j + 1) % SZ(_to[i])] + 1 });
		}
	}
	cout << SZ(ans) << endk;
	REP(i, SZ(ans)) {
		cout << ans[i].first << " " << ans[i].second << endk;
	}
}