#include <fstream>
#include <vector>
#include <algorithm>
#define N 105
using namespace std;

ifstream fin("autostrada.in");
ofstream fout("autostrada.out");

struct lista
{
    int nod, c;
    lista *urm;
}*g[N];

struct Punct
{
    int x,y;
    friend bool operator <(Punct p1, Punct p2)
    {
        if(p1.x!=p2.x)return p1.x<p2.x;
        else return p1.y<p2.y;
    }
};
vector <Punct> v;
void add(int x, int y)
{
    lista*p=new lista;
    p->nod=y;
    p->c=0;
    p->urm=g[x];
    g[x]=p;
}
int n,m;
void citire()
{
    int x,y,k;
    fin>>n>>m;
    for(k=1;k<=m;++k)
    {
        fin>>x>>y;
        add(x,y);
        add(y,x);
    }
}
int t[N], viz[N], niv[N], l[N];
void DFS(int nod)
{
    lista *p;
    int x;
    viz[nod]=1;
    l[nod]=niv[nod];
    for(p=g[nod];p; p=p->urm)
    {
        x=p->nod;
        if(!viz[x])
        {
            niv[x]=niv[nod]+1;
            t[x]=nod;
            DFS(x);
            if(l[nod]>l[x])l[nod]=l[x];
            if(l[x]>niv[nod])p->c=1;
        }
        else
            if(x!=t[nod] && l[nod]>niv[x])
             l[nod]=niv[x];
    }
}
int main()
{
  lista *p;
  citire();
  Punct q;
  for(int i=1;i<=n;i++)
    if(!viz[i])
  {
      niv[i]=1;
      DFS(i);
  }
  int k=0;
  for(int i=1;i<=n;i++)
    for(p=g[i]; p; p=p->urm)
     if(p->c==1) k++;
  fout<<k<<"\n";
  for(int i=1;i<=n;i++)
    for(p=g[i];p;p=p->urm)
     if(p->c==1)
  {
      if(i>p->nod)swap(i,p->nod);
      q.x=i;
      q.y=p->nod;
      v.push_back(q);
  }
  sort(v.begin(), v.end(),less<Punct>());
  for(int i=0;i<k;i++)
    fout<<v[i].x<<" "<<v[i].y<<"\n";
  return 0;
}