#include <bits/stdc++.h>
using namespace std;

#define int long long

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int N,M;
	cin>>N>>M;
	vector<vector<int>>g(N+1);
	for(int i=0;i<M;i++){
		int a,b;
		cin>>a>>b;
		if(i+1==N*(N-1)/2){
			break;
		}
		g[a].push_back(b);
		g[b].push_back(a);
	}
	vector<tuple<int,int,int,int>>c;
	for(int i=1;i<=N;i++){
		vector<int>v(N+1);
		v[i]=-1;
		for(int j:g[i]){
			v[j]=-1;
		}
		for(int j:g[i]){
			for(int k:g[j]){
				if(v[k]<0){
					continue;
				}
				if(v[k]>0){
					c.emplace_back(i,j,v[k],k);
					continue;
				}
				v[k]=j;
			}
		}
	}
	for(auto[a,b,aa,bb]:c){
		vector<int>v(N+1,-1);
		vector<vector<pair<int,int>>>w(2);
		auto dfs=[&](auto self,int i)->void{
			for(int j:g[i]){
				if(v[j]!=-1){
					continue;
				}
				v[j]=v[i];
				self(self,j);
				w[v[i]].emplace_back(i,j);
			}
		};
		v[a]=0;
		v[b]=1;
		v[aa]=0;
		v[bb]=1;
		dfs(dfs,aa);
		dfs(dfs,bb);
		if(count(v.begin(),v.end(),-1)==1){
			vector<pair<int,int>>s;
			for(auto[a,b]:w[0]){
				s.emplace_back(a,b);
			}
			for(auto[a,b]:w[1]){
				s.emplace_back(a,b);
			}
			s.emplace_back(a,aa);
			s.emplace_back(b,bb);
			s.emplace_back(a,b);
			s.emplace_back(aa,bb);
			reverse(w[0].begin(),w[0].end());
			reverse(w[1].begin(),w[1].end());
			for(auto[a,b]:w[0]){
				s.emplace_back(a,b);
			}
			for(auto[a,b]:w[1]){
				s.emplace_back(a,b);
			}
			cout<<s.size()<<'\n';
			for(auto[a,b]:s){
				cout<<a<<' '<<b<<'\n';
			}
			return 0;
		}
	}
	int a=1,b=g[1][0];
	vector<int>v(N+1,-1);
	vector<vector<pair<int,int>>>w(2);
	auto dfs=[&](auto self,int i)->void{
		for(int j:g[i]){
			if(v[j]!=-1){
				continue;
			}
			v[j]=v[i];
			self(self,j);
			w[v[i]].emplace_back(i,j);
		}
	};
	v[a]=0;
	v[b]=1;
	dfs(dfs,a);
	dfs(dfs,b);
	vector<pair<int,int>>s;
	for(auto[a,b]:w[0]){
		s.emplace_back(a,b);
	}
	for(auto[a,b]:w[1]){
		s.emplace_back(a,b);
	}
	s.emplace_back(a,b);
	reverse(w[0].begin(),w[0].end());
	reverse(w[1].begin(),w[1].end());
	for(auto[a,b]:w[0]){
		s.emplace_back(a,b);
	}
	for(auto[a,b]:w[1]){
		s.emplace_back(a,b);
	}
	cout<<s.size()<<'\n';
	for(auto[a,b]:s){
		cout<<a<<' '<<b<<'\n';
	}
	return 0;
}