#include <bits/stdc++.h>
#define TASK "BLUEHOUSE"
#define FAST ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define READFILE freopen(TASK".INP","r",stdin)
#define WRITEFILE freopen(TASK".OUT","w",stdout)
#define For(i,a,b) for(int i=a;i<=b;i++)
#define Rep(i,a,b) for(int i=a;i>=b;i--)
#define pb push_back
#define ENDL '\n'
#define debug(x) cout<<#x<<" = "<<x<<ENDL
#define fi first
#define se second
#define ever (;true;)
#define all(x) x.begin(),x.end()
#define sz(a) ((int)(a).size())
#define ms(a,x) memset(a,x,sizeof(a))
#define int long long

using namespace std;
typedef vector <int> vi;
typedef pair <int,int> ii;
typedef vector <ii> vpi;
typedef pair <int,ii> iii;
const int N = 50010;
const int oo=0x3f;
const int mod=1e9+7;
const int dx[]={0,1,0,-1,0};
int n,m,num[N],low[N],f[N],cnt,scc,tp[N],s[5];
vpi edge;
vi a[N],g[N];
stack<int> st;
void dfs(int u, int p){
    num[u]=low[u]=++cnt;
    st.push(u);
    for (int v:g[u]){
        if (v==p) continue;
        if (num[v]) low[u]=min(low[u],num[v]);
        else {
            dfs(v,u);
            low[u]=min(low[u],low[v]);
            if (low[v]>=num[v]) edge.pb({u,v});
        }
    }
    if (low[u]==num[u]){
        int v;
        scc++;
        f[scc]=u;
        do{
            v=st.top();
            st.pop();
            tp[v]=scc;
        } while (v!=u);
    }
}
void dfs2(int u, int p){
    if (a[u].size()==1 && u!=1) st.push(u);
    for (int v:a[u]){
        if (v==p) continue;
        dfs2(v,u);
    }
}
void init(){
  FAST;
  #ifndef ONLINE_JUDGE
    READFILE;
    WRITEFILE;
  #endif
  cin >> n >> m;
  For(i,1,m){
    int u,v;
    cin >> u >> v;
    g[u].pb(v);
    g[v].pb(u);
  }
}
signed main()
{
  init();
  dfs(1,-1);
  for (ii s : edge){
    int u=s.fi;
    int v=s.se;
    a[tp[u]].pb(tp[v]);
    a[tp[v]].pb(tp[u]);
  }
  dfs2(1,-1);
  stack<ii> ss;
  cnt=0;
  while (st.size()){
    s[++cnt]=st.top();
    st.pop();
    if (cnt==3){
        ss.push({f[s[1]],f[s[3]]});
        cnt=1;
        s[1]=s[2];
    }
  }
  if (cnt==2) ss.push({f[s[1]],f[s[2]]});
  if (cnt==1 || a[1].size()==1) {
    ss.push({f[s[1]],f[1]});
    a[1].pb(2);
  }
  cout << ss.size() << ENDL;
  while (ss.size()){
    cout << ss.top().fi << ' ' << ss.top().se << ENDL;
    ss.pop();
  }
  return 0;
}