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:
import sys
from collections import defaultdict
sys.setrecursionlimit(10**7)
MOD = 10**9+7

def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return sys.stdin.readline().rstrip()
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()


def main():
  n, m = LI()

  if m%2==1:
    print(-1)
    exit()

  graph = defaultdict(set)
  grapht = defaultdict(set)
  for i in range(m):
    a, b = LI()
    a -= 1
    b -= 1
    graph[a].add(b)
    graph[b].add(a)
    grapht[a].add(b)
    grapht[b].add(a)

  graph2 = defaultdict(set)
  visited = [0 for i in range(n)]
  num = [1 for i in range(n)]

  def dfs(x):
    visited[x] = 1

    for nx in graph[x]:
      if not visited[nx]:
        dfs(nx)

    t = set()
    if num[x]==1 and len(grapht[x])%2==0:
      for e in grapht[x]:
        graph2[x].add(e)
        t.add(e)
    elif num[x]==-1 and len(grapht[x])%2==0:
      for j, e in enumerate(grapht[x]):
        if j==len(grapht[x])-1:
          graph2[e].add(x)
          num[e] *= -1
        else:
          graph2[x].add(e)
        t.add(e)
    elif num[x]==1 and len(grapht[x])%2==1:
      for j, e in enumerate(grapht[x]):
        if j==len(grapht[x])-1:
          graph2[e].add(x)
          num[e] *= -1
        else:
          graph2[x].add(e)
        t.add(e)
    elif num[x]==-1 and len(grapht[x])%2==1:
      for e in grapht[x]:
        graph2[x].add(e)
        t.add(e)

    for e in t:
      grapht[x].remove(e)
      grapht[e].remove(x)

  dfs(0)

  for i in range(n):
    for e in graph2[i]:
      print(i+1, e+1)

if __name__ == '__main__':
  main()