#line 1 "a.cpp"
#include<iostream>
#include<algorithm>
using namespace std;
#line 1 "/home/kotatsugame/library/graph/SCC.cpp"
//Strongly Connected Components
#include<vector>
struct SCC{
	int n;
	vector<int>comp,order;
	vector<bool>used;
	vector<vector<int> >G,RG;
	SCC(int _n=0):n(_n),comp(_n,-1),used(_n,false),G(_n),RG(_n){}
	void add_edge(int from,int to)
	{
		G[from].push_back(to);
		RG[to].push_back(from);
	}
	void copy(const vector<vector<int> >&H)
	{
		for(int i=0;i<H.size();i++)
		{
			for(int j=0;j<H[i].size();j++)
			{
				G[i].push_back(H[i][j]);
				RG[H[i][j]].push_back(i);
			}
		}
	}
	int operator[](int u)const{return comp[u];}
	void dfs(int u)
	{
		used[u]=true;
		for(int i=0;i<G[u].size();i++)if(!used[G[u][i]])dfs(G[u][i]);
		order.push_back(u);
	}
	void rdfs(int u,int cnt)
	{
		comp[u]=cnt;
		for(int i=0;i<RG[u].size();i++)if(comp[RG[u][i]]==-1)rdfs(RG[u][i],cnt);
	}
	int build()
	{
		for(int i=0;i<n;i++)if(!used[i])dfs(i);
		int cnt=0;
		for(int i=n-1;i>=0;i--)if(comp[order[i]]==-1)rdfs(order[i],cnt++);
		return cnt;
	}
	int build(vector<vector<int> >&H)
	{
		int ret=build();
		H.assign(ret,vector<int>());
		for(int i=0;i<n;i++)
		{
			for(int j=0;j<G[i].size();j++)
			{
				if(comp[i]!=comp[G[i][j]])
					H[comp[i]].push_back(comp[G[i][j]]);
			}
		}
		return ret;
	}
};
#line 5 "a.cpp"
int N,M;
vector<pair<int,int> >E;
bool vis[2<<17];
vector<int>G[2<<17];
vector<int>vs[2<<17];
vector<int>now;
void dfs(int u)
{
	vis[u]=true;
	now.push_back(u);
	for(int v:G[u])if(!vis[v])
	{
		dfs(v);
	}
}
main()
{
	cin>>N>>M;
	SCC P(N);
	for(int i=0;i<M;i++)
	{
		int u,v;cin>>u>>v;
		u--,v--;
		P.add_edge(u,v);
	}
	vector<vector<int> >H;
	int K=P.build(H);
	for(int i=0;i<N;i++)vs[P[i]].push_back(i);
	for(int i=0;i<K;i++)for(int v:H[i])
	{
		G[i].push_back(v);
		G[v].push_back(i);
	}
	for(int i=0;i<K;i++)if(!vis[i])
	{
		now.clear();
		dfs(i);
		sort(now.begin(),now.end());
		int cnt=0;
		for(int u:now)if(vs[u].size()>=2)cnt++;
		if(cnt==0)
		{
			for(int j=0;j<now.size()-1;j++)
			{
				E.push_back(make_pair(vs[now[j]][0],vs[now[j+1]][0]));
			}
		}
		else
		{
			vector<int>vvs;
			for(int u:now)for(int v:vs[u])vvs.push_back(v);
			int f=vvs.back();
			for(int u:vvs)
			{
				E.push_back(make_pair(f,u));
				f=u;
			}
		}
	}
	cout<<E.size()<<endl;
	for(pair<int,int>p:E)cout<<p.first+1<<" "<<p.second+1<<endl;
}