bool vis[maxn];

int dfn[maxn],low[maxn];

int cnt;

vector<int>gra[maxn];

void cutPoint(int u,int v){

    vis[u]=true;

    dfn[u]=low[u]=++cnt;

    int child=0;

    int sz=gra[u].size();

    for(int i=0;i<sz;i++){

        int v=gra[u][i];

        if(v!=f&&vis[v]){

            low[u]=min(low[u],dfn[v]);

        }else if(!vis[v]){

            child++;

            cutPoint(u,v);

            low[u]=min(low[u],low[v]);

            if(f!=-1&&low[v]>dfn[u]){

                printf("%d-%d\n",u,v);

            }

        }

    }

}