#include <bits/stdc++.h>
#define int long long
#define MIN(x,y) {if (x > (y)) x = (y)}
#define MAX(x,y) {if (x < (y)) x = (y)}
using namespace std;
const int N = 10005;
typedef pair<int,int> ii;

vector<int> a[N];
int n,m,par[N];
int num[N],low[N], cnt = 0;
vector<ii> res;

void dfs(int u)
{
    low[u] = num[u] = ++ cnt;
    for(int i = 0; i < a[u].size(); ++i)
    {
        int v = a[u][i];
        if (v == par[u]) continue;
        if (par[v]) low[u]=min(low[u],num[v]);
        else
        {
            par[v]=u;
            dfs(v);
            low[u]=min(low[u],low[v]);
            if (low[v] == num[v]) res.push_back(ii(u,v));
        }
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    freopen("cbridge.inp","r",stdin);
    freopen("cbridge.out","w",stdout);
    cin >> n >> m;
    for(int i=1; i<=m; ++i)
    {
        int u,v;
        cin >> u >> v;
        a[u].push_back(v);
        a[v].push_back(u);
    }
    for(int i=1; i<=n; ++i)
    {
        if (!par[i])
        {
            par[i]=-1;
            dfs(i);
        }
    }
    cout << res.size() << endl;
    for(ii x : res) cout << x.first << " " << x.second << endl;
    return 0;
}