#include<bits/stdc++.h>
#define N 5005
#define M N*N*2
using namespace std;
int n,m,s,t;
int tot=1,head[N],w[M],nxt[M],to[M];
void addedge(int u,int v,int ww){
	to[++tot]=v;w[tot]=ww;nxt[tot]=head[u];head[u]=tot;
	to[++tot]=u;w[tot]=ww;nxt[tot]=head[v];head[v]=tot;
}
int now[N],d[N];
int col[N];
void dfs(int u,int c){
	col[u]=c;
	for(int i=head[u];i;i=nxt[i]){
		int v=to[i];
		if(!col[v]){
			dfs(v,3-c);
		}
	}
}
void build(){
	s=n+1,t=n+2;
	for(int i=1;i<=n;i++){
		if(col[i]==1){
			for(int j=head[i];j;j=nxt[j]){
				w[j^1]=0;
			}
			addedge(s,i,1);
			w[tot]=0;
		}
		else{
			for(int j=head[i];j;j=nxt[j]){
				w[j]=0;
			}
			addedge(i,t,1);
			w[tot]=0;
		}
	}
}
queue<int> Q;
bool bfs(){
	memset(d,0,sizeof(d));
	while(!Q.empty())Q.pop();
	Q.push(s);d[s]=1;now[s]=head[s];
	while(!Q.empty()){
		int u=Q.front();Q.pop();
		for(int i=head[u];i;i=nxt[i]){
			int v=to[i];
			if(d[v]||w[i]==0)continue;
			d[v]=d[u]+1;
			now[v]=head[v];
			Q.push(v);
			if(v==t)return 1;
		}
	}
	return 0;
}
int dinic(int u,int flow){
	if(u==t){
		return flow;
	}
	int rest=flow,k,i;
	for(int i=head[u];i&&rest;i=nxt[i]){
		int v=to[i];
		if(w[i]&&d[v]==d[u]+1){
			k=dinic(v,min(rest,w[i]));
			if(!k)d[v]=0;
			rest-=k;
			w[i]-=k;
			w[i^1]+=k;
		}
	}
	now[u]=i;
	return flow-rest;
}
int dfn[N],num=0,low[N],stk[N],cnt=0,top=0,scc[N];
void tarjan(int u){
	low[u]=dfn[u]=++num;
	stk[++top]=u;
	for(int i=head[u];i;i=nxt[i]){
		int v=to[i];
		if(w[i]==0)continue;
		if(!dfn[v]){
			tarjan(v);
			low[u]=min(low[u],low[v]); 
		}
		else{
			if(!scc[v]){
				low[u]=min(low[u],dfn[v]);
			}
		}
	}
	if(low[u]==dfn[u]){
		++cnt;
		while(1){
			int p=stk[top];
			scc[p]=cnt;
			top--;
			if(p==u)break;
		}
	}
	return;
}
struct ele{
	int x,y;
}tmp[N];
int size=0;
bool cmp(ele a,ele b){
	if(a.x!=b.x){
		return a.x<b.x;
	}
	else{
		return a.y<b.y;
	}
}
void solve(){
	for(int i=2;i<=tot;i++){
		if(w[i]==1&&col[to[i]]==1){
			if(to[i]!=s&&to[i]!=t&&to[i^1]!=s&&to[i^1]!=t){
				if(scc[to[i]]!=scc[to[i^1]]){
					tmp[++size].x=to[i];
					tmp[size].y=to[i^1];
					if(tmp[size].x>tmp[size].y){
						swap(tmp[size].x,tmp[size].y);
					}
				}
			}
		}
	}
	sort(tmp+1,tmp+size+1,cmp);
	printf("%d\n",size);
	for(int i=1;i<=size;i++){
		printf("%d %d\n",tmp[i].x,tmp[i].y);
	}
	return;
}
queue<int> q;
bool visit[N];
void printfgraph(int s){
	q.push(s);
	memset(visit,0,sizeof(visit));
	while(!q.empty()){
		int u=q.front();q.pop();
		for(int i=head[u];i;i=nxt[i]){
			cout<<"Edge from"<<u<<"to"<<to[i]<<",c="<<w[i]<<endl;
			if(visit[to[i]])continue;
			visit[to[i]]=1;
			q.push(to[i]);
		}
	}
}
void printe(){
	for(int i=2;i<=tot;i++){
		if(w[i])
		printf("from%dto%d,c=%d,colto=%d\n",to[i^1],to[i],w[i],col[to[i]]);
	} 
}
int main()
{
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++){
		int u,v,ww=1;
		scanf("%d%d",&u,&v);
		addedge(u,v,ww);
	}
	for(int i=1;i<=n;i++){
		if(!col[i])dfs(i,1);
	}
	build();
	while(bfs()){
		while(dinic(s,(1<<30)));
	}
	for(int i=n+2;i>=1;i--){
		if(!dfn[i])tarjan(i);
	}
	solve();
	return 0;
}