//8.4 圖的割邊

#include<cstdio>
int n,m,e[9][9],root;
int num[9],low[9],flag[9],index;
int min(int a,int b)
{
    return a<b?a:b;
}
void dfs(int cur,int father)
{
    int child=0,i,j;
    index++;
    num[cur]=index;
    low[cur]=index;
    for(i=1;i<=n;i++)
    {
        if(e[cur][i]==1
 
)
        {
            if(num[i]==0)
            {
                child++;
                dfs(i,cur);
                low[cur]=min(low[cur],low[i]);
                if(low[i]>num[cur])
                    printf("%d-%d\n",cur,i);
            }
            else if(i!=father)
            {
                low[cur]=min(low[cur],num[i]);
            }
        }
    }
}
int
 
 main()
{
    freopen("data.in","r",stdin);
    int i,j,x,y;
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
            e[i][j]=0;
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        e[x][y]=1;
        e[y][x]=1;  
    }
    root=1;
    dfs(1
 
,root);
    return 0;
}