#include <bits/stdc++.h>

using namespace std;

typedef long long int ll;
typedef double ld;

typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;

#define PB push_back
#define FOR(prom, a, b) for ( ll prom = (a); prom < (ll)(b); ++prom )
#define F(a) FOR(i,0,a)
#define FF(a) FOR(j,0,a)

#define EPS (1e-10)

ll N,M;
stack<ll> st;
vector<bool> visited;
vector<vi> result,adj;
void dfsSCC(int v,bool first){
	visited[v]=true;
	if(!first)result[result.size()-1].PB(v);
	for(ll n:adj[v]) if(!visited[n]) dfsSCC(n,first);
	if(first)st.push(v);
}
vector<vi> strongComponents(vector<vi> &g){
	N=g.size();
	adj=g;
	visited=vector<bool>(N,0);
	result.clear();
	st=stack<ll>();
	F(N)if(!visited[i])dfsSCC(i,true);
	vector<vi> adjinv(N);
	F(N)for(ll n:adj[i])adjinv[n].PB(i);
	swap(adj,adjinv);
	visited=vector<bool>(N,0);
	while(!st.empty()){
		ll v = st.top(); st.pop();
		if(!visited[v]){
			result.PB(vi());
			dfsSCC(v,false);
		}
	}
	return result;
}

int main () {
	srand(time(NULL));
	ios::sync_with_stdio(false);
	
	ll N;
	while(cin>>N>>M){
		vector<vi> g(N);
		vii e(M);
		F(M){
			ll c,b;cin>>c>>b;c--;b--;
			g[c].PB(b);
			e[i]={c,b};
		}
		vector<vi> res = strongComponents(g);
		vi comp(N);
		F(res.size()) for(ll n:res[i]){comp[n]=i;}
		vi out(res.size());
		vi in(res.size());
		F(M){
			ll ca=comp[e[i].first];
			ll cb=comp[e[i].second];
			if(ca!=cb){
				out[ca]++;
				in[cb]++;
			}
		}
		vi src,dst;
		F(res.size()){
			if(out[i]==0)src.PB(i);
			if(in[i]==0)dst.PB(i);
		}
		if(src.size()==1&&dst.size()==1&&src[0]==dst[0]){
			cout<<0<<endl;
			continue;
		}
		vector<vi> dag;
		ll iii=0;
		vii ans;
		do{
			dag=vector<vi> (res.size());
			F(M){
				ll ca=comp[e[i].first];
				ll cb=comp[e[i].second];
				if(ca!=cb){
					dag[ca].PB(cb);
				}
			}
			ans.clear();
			ll i=src.size(),j=dst.size();
			if(iii!=0){
				random_shuffle(src.begin(),src.end());
				random_shuffle(dag.begin(),dag.end());
			}
			iii++;
			while(i!=0 || j!=0){
				if(i!=0)i--;
				if(j!=0)j--;
				ll r=comp[res[src[i]][0]];
				ll t=comp[res[dst[j]][0]];
				dag[r].PB(t);
				ans.PB({res[src[i]][0]+1,res[dst[j]][0]+1});
			}
		}while(strongComponents(dag).size()!=1);
		cout<<ans.size()<<endl;
		for(ii q:ans){
			cout<<q.first<<' '<<q.second<<endl;
		}
	}
	
	return 0;
}