#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000

vector<int> A,B;

void go(vector<int> ind,vector<int> a,vector<int> b){
	int n = ind.size();
	sort(ind.begin(),ind.end());
	
	scc_graph S(n);
	
	rep(i,a.size()){
		int x = distance(ind.begin(),lower_bound(ind.begin(),ind.end(),a[i]));
		int y = distance(ind.begin(),lower_bound(ind.begin(),ind.end(),b[i]));
		S.add_edge(x,y);
	}
	
	vector<vector<int>>  s = S.scc();
	
	
	rep(i,s.size()){
	
		if(i+1!=s.size()){
			A.push_back(ind[s[i][0]]);
			B.push_back(ind[s[i+1][0]]);
		}
		if(s[i].size()>=2){
			rep(j,s[i].size()){
				
				int x = s[i][j];
				int y = s[i][(j+1)%s[i].size()];
				A.push_back(ind[x]);
				B.push_back(ind[y]);
				
			}
		}
	}
	
}

int main(){
	
	int N,M;
	cin>>N>>M;
	
	vector<int> a(M),b(M);
	
	dsu D(N);
	
	rep(i,M){
		scanf("%d %d",&a[i],&b[i]);
		a[i]--;b[i]--;
		D.merge(a[i],b[i]);
	}
	
	vector<int> pos(N);
	vector<vector<int>> ret = D.groups();
	rep(i,ret.size()){
		rep(j,ret[i].size()){
			pos[ret[i][j]] = i;
		}
	}
//	cout<<'a'<<endl;
	vector<vector<int>> aa(ret.size()),bb(ret.size());
	
	rep(i,M){
		int ind = pos[a[i]];
		aa[ind].push_back(a[i]);
		bb[ind].push_back(b[i]);		
	}
	
	rep(i,ret.size()){
		go(ret[i],aa[i],bb[i]);
	}
	//cout<<'a'<<endl;
	cout<<A.size()<<endl;
	rep(i,A.size()){
		printf("%d %d\n",A[i]+1,B[i]+1);
	}
	
    return 0;
}