#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
#define MAXN 10100
#define MAXM 150150
#define inf 1e9
inline int read()
{int x=0;bool t=false;char ch=getchar();while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();if(ch=='-')t=true,ch=getchar();while(ch<='9'&&ch>='0')x=x*10+ch-48,ch=getchar();return t?-x:x;
}
struct Line{int v,next,w;}e[MAXM<<1];
int h[MAXN],cnt=2;
inline void Add(int u,int v,int w)
{e[cnt]=(Line){v,h[u],w};h[u]=cnt++;e[cnt]=(Line){u,h[v],0};h[v]=cnt++;
}
int S,T,level[MAXN];
bool bfs()
{for(int i=S;i<=T;++i)level[i]=0;queue<int> Q;level[S]=1;Q.push(S);while(!Q.empty()){int u=Q.front();Q.pop();for(int i=h[u];i;i=e[i].next)if(e[i].w&&!level[e[i].v])level[e[i].v]=level[u]+1,Q.push(e[i].v);}return level[T];
}
int cur[MAXN];
int dfs(int u,int flow)
{if(u==T||!flow)return flow;int ret=0;for(int &i=cur[u];i;i=e[i].next){int v=e[i].v,d;if(e[i].w&&level[v]==level[u]+1){d=dfs(v,min(flow,e[i].w));ret+=d;flow-=d;e[i].w-=d;e[i^1].w+=d;if(!flow)break;}}if(!ret)level[u]=0;return ret;
}
int Dinic()
{int ret=0;while(bfs()){for(int i=S;i<=T;++i)cur[i]=h[i];ret+=dfs(S,inf);}return ret;
}
vector<pair<int,int> > Ans;
vector<int> E[MAXN];
int n,m,col[MAXN];
void pre(int u,int c){col[u]=c;for(int v:E[u])if(!col[v])pre(v,c^1);}
int dfn[MAXN],low[MAXN],tim,G[MAXN],gr;
int St[MAXN],top;bool ins[MAXN];
void Tarjan(int u)
{dfn[u]=low[u]=++tim;St[++top]=u;ins[u]=true;for(int i=h[u];i;i=e[i].next){int v=e[i].v;if(!e[i].w)continue;if(!dfn[v])Tarjan(v),low[u]=min(low[u],low[v]);else if(ins[v])low[u]=min(low[u],dfn[v]);}if(dfn[u]==low[u]){++gr;int v;do{v=St[top--];G[v]=gr;ins[v]=false;}while(u!=v);}
}
int main()
{n=read();m=read();for(int i=1;i<=m;++i){int u=read(),v=read();E[u].push_back(v);E[v].push_back(u);}for(int i=1;i<=n;++i)if(!col[i])pre(i,2);S=0;T=n+1;for(int i=1;i<=n;++i)if(col[i]==2){Add(S,i,1);for(int v:E[i])Add(i,v,1);}else Add(i,T,1);int ret=Dinic();for(int i=S;i<=T;++i)if(!dfn[i])Tarjan(i);for(int u=1;u<=n;++u)if(col[u]==2)for(int i=h[u];i;i=e[i].next){int v=e[i].v;if(e[i].w)continue;if(v==S||v==T)continue;if(G[u]!=G[v])Ans.push_back(u<v?make_pair(u,v):make_pair(v,u));}sort(Ans.begin(),Ans.end());printf("%d\n",(int)Ans.size());for(auto a:Ans)printf("%d %d\n",a.first,a.second);return 0;
}