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 PYTHON3):

Solution:
class Bridge:
    def __init__(self, nodeA, nodeB):
        self.edges = [Edge(nodeA, self), Edge(nodeB, self)]
        nodeA.addEdge(self.edges[1])
        nodeB.addEdge(self.edges[0])
        self.dir = True
        self.vec = None
    def __repr__(self):
        return str((self.vec, self.dir))

class Edge:
    def __init__(self, node, bridge):
        self.bridge = bridge
        self.node = node
    def another(self):
        return self.bridge.edges[1 if self.bridge.edges[0] == self else 0]

class Node:
    def __init__(self, id):
        self.id = id
        self.edges = []
        self.parent = None
        self.judge = True
    def addEdge(self, edge):
        self.edges.append(edge)
    def __repr__(self):
        return str((self.id, None if self.parent is None else self.parent.node.id, self.judge))

N, M = map(int, input().split())

nodes = [Node(i) for i in range(N+1)]
bridges = []
for A, B in (map(int, input().split()) for _ in range(M)):
    bridges.append(Bridge(nodes[A], nodes[B]))

s = [(0, nodes[1])]
idx = 0
while len(s) > 0:
    level, cur = s.pop()

    nxtlevel = level + 1
    for nxt in cur.edges:
        if nxt.bridge.vec is None:
            cur.judge ^= True
            nxt.bridge.vec = (cur.id, nxt.node.id)
            if nxt.node.parent is None:
                nxt.node.parent = nxt.another()
                s.append((nxtlevel, nxt.node))

    if len(s) > 0:
        nl = s[-1][0]
    else:
        nl = 1
    while level >= nl:
        if not cur.judge:
            cur.judge ^= True
            cur.parent.node.judge ^= True
            cur.parent.bridge.dir ^= True
        level -= 1
        cur = cur.parent.node
  
if nodes[1].judge:
    for br in bridges:
        if br.dir:
            print("{} {}".format(br.vec[0], br.vec[1]))
        else:
            print("{} {}".format(br.vec[1], br.vec[0]))
else:
    print("-1")