#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define mk make_pair
#define ll long long
#define space putchar(' ')
#define enter putchar('\n')
using namespace std;

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

inline int rd() { int x = 0, f = 1; char c = getchar(); while (!isdigit(c)) f = c == '-' ? -1 : f, c = getchar(); while (isdigit(c)) x = (x<<3)+(x<<1)+(c^48), c = getchar(); return x*f; }
template <typename T> inline void write(T x) { if (x < 0) x = -x, putchar('-'); if (x > 9) write(x/10); putchar(x%10+48); }

const int N = 5e5+5;
struct edge { int to, nxt; } e[N];
int n, m, tot = 1, idx, hd[N], bg[N], dfn[N], low[N];

void add(int x, int y) { e[++tot] = {y, hd[x]}, hd[x] = tot; }

void tarjan(int x, int k) {
    dfn[x] = low[x] = ++idx;
    for (int i = hd[x]; i; i = e[i].nxt) {
        int y = e[i].to;
        if (!dfn[y]) {
            tarjan(y, i);
            low[x] = min(low[x], low[y]);
            if (low[y] > dfn[x]) bg[i] = bg[i^1] = 1;
        }
        else if (i != (k^1)) low[x] = min(low[x], dfn[y]);
    }
}

int main() {
    #ifdef wwm
    freopen("a.in", "r", stdin);
    freopen("a.out", "w", stdout);
    #endif
    cin >> n >> m;
    while (m--) {
        int x, y, z; cin >> x >> y;
        add(x, y), add(y, x);
    }
    for (int i = 1; i <= n; ++i) if (!dfn[i]) tarjan(i, 0);
    for (int i = 2; i <= tot; i += 2) if (bg[i]) cout << e[i^1].to << ' ' << e[i].to << '\n';
    return 0;
}