#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

#define ff first
#define ss second
#define y1 y111
#define X first
#define Y second
#define mk make_pair
#define inb push_back
#define all(v) v.begin(), v.end()

const int MAXN = (int)1e6 + 9, MAXN1 = (int)2e4 + 7;
const int INFint = (int)1e9 + 7, P = 31;
const ll INFll = (ll)1e18 + 7, MOD = (ll)1e9 + 7;
const double INFfl = 1e18 * 4 + 7;
const double EPS = 1e-7;
const double PI = atan2(0, -1);

vector < pair <int, int> > g[MAXN];
int n, m, x, y, t, t_in[MAXN], up[MAXN], col, color[MAXN], mx_cnt, cnt_nom;
int cnt[MAXN], w[MAXN];
bool used[MAXN], in_ans[MAXN], most[MAXN];


vector < pair < int, pair <int, int> > > ans;

int solve();

int main()
{
#define TASK ""
#ifdef _DEBUG
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#else
    //freopen(TASK".in", "r", stdin), freopen(TASK".out", "w", stdout);
#endif
    solve();
}

const int STRBUF = (int)1e6 + 7;
char buf[STRBUF];
string get_str()
{
    scanf(" %s", buf);
    return string(buf);
}

void dfs (int v, int nom)
{
    used[v] = 1;
    t++;
    t_in[v] = t;
    up[v] = t;

    for (int i = 0; i < g[v].size(); ++i)
    {
        if (nom == g[v][i].ss)
            continue;
        int u = g[v][i].ff;
        if (used[u])
        {
            up[v] = min(up[v], t_in[u]);
            continue;
        }
        dfs(u, g[v][i].ss);
        up[v] = min(up[v], up[u]);
        if (t_in[v] < up[u])
        {
            most[g[v][i].ss] = 1;
        }
    }
}

void dfs1(int v)
{
    color[v] = col;
    for (int i = 0; i < g[v].size(); ++i)
    {
        if (!color[g[v][i].ff] && !most[g[v][i].ss])
        {
            //cout << col << ' ' << g[v][i].ff << ' ' << g[v][i].ss << '\n';
            dfs1(g[v][i].ff);
        }
    }
}

void dfs_fin (int v)
{
    int u;
    used[v] = 1;
    for (int i = 0; i < g[v].size(); ++i)
    {
        u = g[v][i].ff;
        if (!in_ans[g[v][i].ss])
        {
            if (!most[g[v][i].ss])
            {
                ans.push_back({g[v][i].ss, {v, u}});
            }
            else
            {
                ans.push_back({g[v][i].ss, {u, v}});
            }
            in_ans[g[v][i].ss] = 1;
        }
        if (!used[u])
            dfs_fin(u);
    }
}

int solve()
{
    int n, m;

    scanf("%d%d", &n, &m);
    for (int i = 0; i < m; ++i)
    {
        scanf("%d%d", &x, &y);
        g[x].push_back({y, i});
        g[y].push_back({x, i});
    }

    dfs(1, -1);
    for (int i = 1; i <= n; ++i)
    {
        if (color[i])
            continue;
        col++;
        dfs1(i);
    }

    for (int i = 1; i <= n; ++i)
    {
        cnt[color[i]]++;
        mx_cnt = max(mx_cnt, cnt[color[i]]);
        w[color[i]] = i;
        if (mx_cnt == cnt[color[i]])
        {
            cnt_nom = color[i];
        }
    }

    memset(used, 0, sizeof(used));
    dfs_fin(w[cnt_nom]);

    sort(ans.begin(), ans.end());

    printf("%d\n", cnt[cnt_nom]);

    for (int i = 0; i < ans.size(); ++i)
        printf("%d %d\n", ans[i].ss.ff, ans[i].ss.ss);

    return 0;
}