Problem: You are given a simple connected undirected graph with N vertices and M edges. The vertices are numbered 1 to N, and the i-th edge connects Vertex A_i and Vertex B_i. Takahashi will assign one of the two possible directions to each of the edges in the graph to make a directed graph. Determine if it is possible to make a directed graph with an even number of edges going out from every vertex. If the answer is yes, construct one such graph.

Constraints

* 2 \leq N \leq 10^5
* N-1 \leq M \leq 10^5
* 1 \leq A_i,B_i \leq N (1\leq i\leq M)
* The given graph is simple and connected.

Input

Input is given from Standard Input in the following format:


N M
A_1 B_1
:
A_M B_M


Output

If it is impossible to assign directions to satisfy the requirement, print -1. Otherwise, print an assignment of directions that satisfies the requirement, in the following format:


C_1 D_1
:
C_M D_M


Here each pair (C_i, D_i) means that there is an edge directed from Vertex C_i to Vertex D_i. The edges may be printed in any order.

Examples

Input

4 4
1 2
2 3
3 4
4 1


Output

1 2
1 4
3 2
3 4


Input

5 5
1 2
2 3
3 4
2 5
4 5


Output

-1

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
using namespace std;
vector<pair<int,int> > a[100005],adj;
int n,m;
int f[100005],con[100005];
bool vis[100005];
void dfs(int v){
	vis[v]=true;
	con[v]+=f[v];
	for(int i=0;i<a[v].size();i++){
		int q=a[v][i].first;
		if(!vis[q]){
			dfs(q);
			con[v]+=con[q];
			if(con[q]%2!=0)
				swap(adj[a[v][i].second].first,adj[a[v][i].second].second);
		}
	}
}
int main (){
	cin>>n>>m;
	for(int i=0;i<m;i++){
		int u,v;
		cin>>u>>v;
			f[u]++; 	
		a[u].push_back(make_pair(v,i));
		a[v].push_back(make_pair(u,i));	
		adj.push_back(make_pair(u,v));
	}
	if(m%2!=0){
		cout<<"-1";
		return 0;
	}
	dfs(1);
	for(int i=0;i<adj.size();i++){
		cout<<adj[i].first<<" "<<adj[i].second<<endl;
	}
}