#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define i1 __int128
#define pii pair<int, int>
#define pll pair<ll, ll>
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define ep emplace
#define eb emplace_back
#define all(v) v.begin(), v.end()

using namespace std;

template<typename types>
void read(types &x) {
    x = 0; char c = getchar(); int f = 1;
    while (!isdigit(c)) { if (c == '-') f = -1; c = getchar(); }
    while (isdigit(c)) x = x * 10 + c - '0', c = getchar();
    x *= f; return;
}
void read() {}
template<typename types, typename... Args>
void read(types &x, Args&... args) {
    read(x), read(args...);
    return;
}
template<typename types>
void write(types x) {
    if (x < 0) putchar('-'), x = -x;
    types k = x / 10;
    if (k) write(k);
    putchar(x - k * 10 + '0');
    return;
}
void print() { puts(""); }
template<typename types, typename... Args>
void print(types x, Args... args) {
    write(x), putchar(' '), print(args...);
    return;
}

const int MAXN = 1e5 + 10;
const int MAXM = 1e6 + 10;

int n, m;
struct Edge {
    int x, y;
} e[MAXM];
int head[MAXN], to[MAXM], w[MAXM], nxt[MAXM], idx = 1;
int dfn[MAXN], low[MAXN], timecnt;
vector<int> v;

void addedge(int x, int y, int z) {
    nxt[++idx] = head[x];
    to[idx] = y;
    w[idx] = z;
    head[x] = idx;
    return;
}
void dfs(int x, int from) {
    dfn[x] = low[x] = ++timecnt;
    for (int i = head[x]; i; i = nxt[i]) {
        if (i == (from ^ 1)) continue;
        int y = to[i];
        if (!dfn[y]) {
            dfs(y, i);
            low[x] = min(low[y], low[y]);
            if (low[y] > dfn[x]) v.eb(w[i]);
        }
        else low[x] = min(low[x], dfn[y]);
    }
    return;
}

int main() {
    ios:: sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    read(n, m);
    for (int i = 1; i <= m; ++i) {
        read(e[i].x, e[i].y);
        addedge(e[i].x, e[i].y, i), addedge(e[i].y, e[i].x, i);
    }
    for (int i = 1; i <= n; ++i)
        if (!dfn[i]) dfs(i, 0);
    sort(all(v)), v.erase(unique(all(v)), v.end());
    for (int i : v) print(e[i].x, e[i].y);
    return 0;
}