//qoj995 tarjan-bridge
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int N = 1e5, M = 1e6 + 10;
int n, m, ex[M], ey[M];
int hd[N], eg[M], nx[M], tot = 1;
int dfn[N], low[N], cnt, isb[M], vis[M];

void add(int u, int v){
	eg[++tot] = v;
	nx[tot] = hd[u];
	hd[u] = tot;
}
// void tg(int x){
	// dfn[x] = low[x] = ++ cnt;
	// for(int i = hd[x]; i; i = nx[i]){
		// if(vis[i]){
			// continue;
		// }
		// int y = eg[i];
		// vis[i] = vis[i^1] = 1;
		// if(!dfn[y]){
			// tg(y);
			// low[x] = min(low[x], low[y]);
			// if(low[y] > dfn[x]){
				// isb[i] = 1;
			// }
		// } else {
			// low[x] = min(low[x], dfn[y]);
		// }
	// }
// }

void tg(int x){
	low[x] = dfn[x] = ++ cnt;
	for(int i = hd[x]; i; i = nx[i]){
		if(vis[i]) continue;
		int y = eg[i];
		vis[i] = vis[i^1] = 1;
		if(!dfn[y]){
			tg(y);
			low[x] = min(low[x], low[y]);
			if(low[y] > dfn[x]){
				isb[i] = 1;
			}
		} else if(dfn[y] < dfn[x]){
			low[x] = min(low[x], dfn[y]);
		}
	}
}

int main(){
	scanf("%d%d", &n, &m);
	for(int i = 1; i <= m; ++ i){
		int u, v;
		scanf("%d%d", &u, &v);
		add(u, v);
		add(v, u);
		ex[i] = u;
		ey[i] = v;
	}
	for(int i = 1; i <= n; ++ i){
		if(!dfn[i]){
			tg(i);
		}
	}
	for(int i = 1; i <= m; ++ i){
		if(isb[i*2]){
			printf("%d %d\n", ex[i], ey[i]);
		}
	}
	return 0;
}