Problem: Student Vladislav came to his programming exam completely unprepared as usual. He got a question about some strange algorithm on a graph — something that will definitely never be useful in real life. He asked a girl sitting next to him to lend him some cheat papers for this questions and found there the following definition:

The minimum spanning tree T of graph G is such a tree that it contains all the vertices of the original graph G, and the sum of the weights of its edges is the minimum possible among all such trees.

Vladislav drew a graph with n vertices and m edges containing no loops and multiple edges. He found one of its minimum spanning trees and then wrote for each edge its weight and whether it is included in the found tree or not. Unfortunately, the piece of paper where the graph was painted is gone and the teacher is getting very angry and demands to see the original graph. Help Vladislav come up with a graph so that the information about the minimum spanning tree remains correct.

Input

The first line of the input contains two integers n and m (<image>) — the number of vertices and the number of edges in the graph.

Each of the next m lines describes an edge of the graph and consists of two integers aj and bj (1 ≤ aj ≤ 109, bj = {0, 1}). The first of these numbers is the weight of the edge and the second number is equal to 1 if this edge was included in the minimum spanning tree found by Vladislav, or 0 if it was not.

It is guaranteed that exactly n - 1 number {bj} are equal to one and exactly m - n + 1 of them are equal to zero.

Output

If Vladislav has made a mistake and such graph doesn't exist, print  - 1.

Otherwise print m lines. On the j-th line print a pair of vertices (uj, vj) (1 ≤ uj, vj ≤ n, uj ≠ vj), that should be connected by the j-th edge. The edges are numbered in the same order as in the input. The graph, determined by these edges, must be connected, contain no loops or multiple edges and its edges with bj = 1 must define the minimum spanning tree. In case there are multiple possible solutions, print any of them.

Examples

Input

4 5
2 1
3 1
4 0
1 1
5 0


Output

2 4
1 4
3 4
3 1
3 2


Input

3 3
1 0
2 1
3 1


Output

-1

Solution (in PYTHON3):

Solution:
import sys
from math import gcd,sqrt,ceil,log2
from collections import defaultdict,Counter,deque
from bisect import bisect_left,bisect_right
import math
sys.setrecursionlimit(2*10**5+10)
import heapq
from itertools import permutations

# input=sys.stdin.readline
# def print(x):
#     sys.stdout.write(str(x)+"\n")

# sys.stdin = open('input.txt', 'r')
# sys.stdout = open('output.txt', 'w')
import os
import sys
from io import BytesIO, IOBase

BUFSIZE = 8192

aa='abcdefghijklmnopqrstuvwxyz'
class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")

# import sys
# import io, os
# input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline
def get_sum(bit,i):
    s = 0

    i+=1
    while i>0:
        s+=bit[i]
        i-=i&(-i)

    return s

def update(bit,n,i,v):
    i+=1

    while i<=n:
        bit[i]+=v
        i+=i&(-i)


def modInverse(b,m):
    g = math.gcd(b, m)
    if (g != 1):
        return -1
    else:
        return pow(b, m - 2, m)

def primeFactors(n):

    sa = []
    # sa.add(n)
    while n % 2 == 0:
        sa.append(2)
        n = n // 2


    for i in range(3,int(math.sqrt(n))+1,2):


        while n % i== 0:
            sa.append(i)
            n = n // i

    # sa.add(n)
    if n > 2:
        sa.append(n)
    return sa


def seive(n):

    pri = [True]*(n+1)
    p = 2
    while p*p<=n:

        if pri[p] == True:

            for i in range(p*p,n+1,p):
                pri[i] = False

        p+=1

    return pri

def check_prim(n):

    if n<0:
        return False
    for i in range(2,int(sqrt(n))+1):
        if n%i == 0:
            return False

    return True


def getZarr(string, z):
    n = len(string)

    # [L,R] make a window which matches
    # with prefix of s
    l, r, k = 0, 0, 0
    for i in range(1, n):

        # if i>R nothing matches so we will calculate.
        # Z[i] using naive way.
        if i > r:
            l, r = i, i

            # R-L = 0 in starting, so it will start
            # checking from 0'th index. For example,
            # for "ababab" and i = 1, the value of R
            # remains 0 and Z[i] becomes 0. For string
            # "aaaaaa" and i = 1, Z[i] and R become 5
            while r < n and string[r - l] == string[r]:
                r += 1
            z[i] = r - l
            r -= 1
        else:

            # k = i-L so k corresponds to number which
            # matches in [L,R] interval.
            k = i - l

            # if Z[k] is less than remaining interval
            # then Z[i] will be equal to Z[k].
            # For example, str = "ababab", i = 3, R = 5
            # and L = 2
            if z[k] < r - i + 1:
                z[i] = z[k]

                # For example str = "aaaaaa" and i = 2,
            # R is 5, L is 0
            else:

                # else start from R and check manually
                l = i
                while r < n and string[r - l] == string[r]:
                    r += 1
                z[i] = r - l
                r -= 1

def search(text, pattern):

    # Create concatenated string "P$T"
    concat = pattern + "$" + text
    l = len(concat)


    z = [0] * l
    getZarr(concat, z)

    ha = []
    for i in range(l):


        if z[i] == len(pattern):
            ha.append(i - len(pattern) - 1)


    return ha


# n,k = map(int,input().split())
# l = list(map(int,input().split()))

#
# n = int(input())
# l = list(map(int,input().split()))
#
# hash = defaultdict(list)
# la = []
#
# for i in range(n):
#     la.append([l[i],i+1])
#
# la.sort(key = lambda x: (x[0],-x[1]))
# ans = []
# r = n
# flag = 0
# lo = []
# ha = [i for i in range(n,0,-1)]
# yo = []
# for a,b in la:
#
#    if a == 1:
#        ans.append([r,b])
#        # hash[(1,1)].append([b,r])
#        lo.append((r,b))
#        ha.pop(0)
#        yo.append([r,b])
#        r-=1
#
#    elif a == 2:
#        # print(yo,lo)
#        # print(hash[1,1])
#        if lo == []:
#            flag = 1
#            break
#        c,d = lo.pop(0)
#        yo.pop(0)
#        if b>=d:
#            flag = 1
#            break
#        ans.append([c,b])
#        yo.append([c,b])
#
#
#
#    elif a == 3:
#
#            if yo == []:
#                flag = 1
#                break
#            c,d = yo.pop(0)
#            if b>=d:
#                flag = 1
#                break
#            if ha == []:
#                flag = 1
#                break
#
#            ka = ha.pop(0)
#
#            ans.append([ka,b])
#            ans.append([ka,d])
#            yo.append([ka,b])
#
# if flag:
#     print(-1)
# else:
#     print(len(ans))
#     for a,b in ans:
#         print(a,b)
def mergeIntervals(arr):

    # Sorting based on the increasing order
    # of the start intervals
    arr.sort(key = lambda x: x[0])

    # array to hold the merged intervals
    m = []
    s = -10000
    max = -100000
    for i in range(len(arr)):
        a = arr[i]
        if a[0] > max:
            if i != 0:
                m.append([s,max])
            max = a[1]
            s = a[0]
        else:
            if a[1] >= max:
                max = a[1]

    #'max' value gives the last point of
    # that particular interval
    # 's' gives the starting point of that interval
    # 'm' array contains the list of all merged intervals

    if max != -100000 and [s, max] not in m:
        m.append([s, max])
    return m
class SortedList:
    def __init__(self, iterable=[], _load=200):
        """Initialize sorted list instance."""
        values = sorted(iterable)
        self._len = _len = len(values)
        self._load = _load
        self._lists = _lists = [values[i:i + _load] for i in range(0, _len, _load)]
        self._list_lens = [len(_list) for _list in _lists]
        self._mins = [_list[0] for _list in _lists]
        self._fen_tree = []
        self._rebuild = True

    def _fen_build(self):
        """Build a fenwick tree instance."""
        self._fen_tree[:] = self._list_lens
        _fen_tree = self._fen_tree
        for i in range(len(_fen_tree)):
            if i | i + 1 < len(_fen_tree):
                _fen_tree[i | i + 1] += _fen_tree[i]
        self._rebuild = False

    def _fen_update(self, index, value):
        """Update `fen_tree[index] += value`."""
        if not self._rebuild:
            _fen_tree = self._fen_tree
            while index < len(_fen_tree):
                _fen_tree[index] += value
                index |= index + 1

    def _fen_query(self, end):
        """Return `sum(_fen_tree[:end])`."""
        if self._rebuild:
            self._fen_build()

        _fen_tree = self._fen_tree
        x = 0
        while end:
            x += _fen_tree[end - 1]
            end &= end - 1
        return x

    def _fen_findkth(self, k):
        """Return a pair of (the largest `idx` such that `sum(_fen_tree[:idx]) <= k`, `k - sum(_fen_tree[:idx])`)."""
        _list_lens = self._list_lens
        if k < _list_lens[0]:
            return 0, k
        if k >= self._len - _list_lens[-1]:
            return len(_list_lens) - 1, k + _list_lens[-1] - self._len
        if self._rebuild:
            self._fen_build()

        _fen_tree = self._fen_tree
        idx = -1
        for d in reversed(range(len(_fen_tree).bit_length())):
            right_idx = idx + (1 << d)
            if right_idx < len(_fen_tree) and k >= _fen_tree[right_idx]:
                idx = right_idx
                k -= _fen_tree[idx]
        return idx + 1, k

    def _delete(self, pos, idx):
        """Delete value at the given `(pos, idx)`."""
        _lists = self._lists
        _mins = self._mins
        _list_lens = self._list_lens

        self._len -= 1
        self._fen_update(pos, -1)
        del _lists[pos][idx]
        _list_lens[pos] -= 1

        if _list_lens[pos]:
            _mins[pos] = _lists[pos][0]
        else:
            del _lists[pos]
            del _list_lens[pos]
            del _mins[pos]
            self._rebuild = True

    def _loc_left(self, value):
        """Return an index pair that corresponds to the first position of `value` in the sorted list."""
        if not self._len:
            return 0, 0

        _lists = self._lists
        _mins = self._mins

        lo, pos = -1, len(_lists) - 1
        while lo + 1 < pos:
            mi = (lo + pos) >> 1
            if value <= _mins[mi]:
                pos = mi
            else:
                lo = mi

        if pos and value <= _lists[pos - 1][-1]:
            pos -= 1

        _list = _lists[pos]
        lo, idx = -1, len(_list)
        while lo + 1 < idx:
            mi = (lo + idx) >> 1
            if value <= _list[mi]:
                idx = mi
            else:
                lo = mi

        return pos, idx

    def _loc_right(self, value):
        """Return an index pair that corresponds to the last position of `value` in the sorted list."""
        if not self._len:
            return 0, 0

        _lists = self._lists
        _mins = self._mins

        pos, hi = 0, len(_lists)
        while pos + 1 < hi:
            mi = (pos + hi) >> 1
            if value < _mins[mi]:
                hi = mi
            else:
                pos = mi

        _list = _lists[pos]
        lo, idx = -1, len(_list)
        while lo + 1 < idx:
            mi = (lo + idx) >> 1
            if value < _list[mi]:
                idx = mi
            else:
                lo = mi

        return pos, idx

    def add(self, value):
        """Add `value` to sorted list."""
        _load = self._load
        _lists = self._lists
        _mins = self._mins
        _list_lens = self._list_lens

        self._len += 1
        if _lists:
            pos, idx = self._loc_right(value)
            self._fen_update(pos, 1)
            _list = _lists[pos]
            _list.insert(idx, value)
            _list_lens[pos] += 1
            _mins[pos] = _list[0]
            if _load + _load < len(_list):
                _lists.insert(pos + 1, _list[_load:])
                _list_lens.insert(pos + 1, len(_list) - _load)
                _mins.insert(pos + 1, _list[_load])
                _list_lens[pos] = _load
                del _list[_load:]
                self._rebuild = True
        else:
            _lists.append([value])
            _mins.append(value)
            _list_lens.append(1)
            self._rebuild = True

    def discard(self, value):
        """Remove `value` from sorted list if it is a member."""
        _lists = self._lists
        if _lists:
            pos, idx = self._loc_right(value)
            if idx and _lists[pos][idx - 1] == value:
                self._delete(pos, idx - 1)

    def remove(self, value):
        """Remove `value` from sorted list; `value` must be a member."""
        _len = self._len
        self.discard(value)
        if _len == self._len:
            raise ValueError('{0!r} not in list'.format(value))

    def pop(self, index=-1):
        """Remove and return value at `index` in sorted list."""
        pos, idx = self._fen_findkth(self._len + index if index < 0 else index)
        value = self._lists[pos][idx]
        self._delete(pos, idx)
        return value

    def bisect_left(self, value):
        """Return the first index to insert `value` in the sorted list."""
        pos, idx = self._loc_left(value)
        return self._fen_query(pos) + idx

    def bisect_right(self, value):
        """Return the last index to insert `value` in the sorted list."""
        pos, idx = self._loc_right(value)
        return self._fen_query(pos) + idx

    def count(self, value):
        """Return number of occurrences of `value` in the sorted list."""
        return self.bisect_right(value) - self.bisect_left(value)

    def __len__(self):
        """Return the size of the sorted list."""
        return self._len

    def __getitem__(self, index):
        """Lookup value at `index` in sorted list."""
        pos, idx = self._fen_findkth(self._len + index if index < 0 else index)
        return self._lists[pos][idx]

    def __delitem__(self, index):
        """Remove value at `index` from sorted list."""
        pos, idx = self._fen_findkth(self._len + index if index < 0 else index)
        self._delete(pos, idx)

    def __contains__(self, value):
        """Return true if `value` is an element of the sorted list."""
        _lists = self._lists
        if _lists:
            pos, idx = self._loc_left(value)
            return idx < len(_lists[pos]) and _lists[pos][idx] == value
        return False

    def __iter__(self):
        """Return an iterator over the sorted list."""
        return (value for _list in self._lists for value in _list)

    def __reversed__(self):
        """Return a reverse iterator over the sorted list."""
        return (value for _list in reversed(self._lists) for value in reversed(_list))

    def __repr__(self):
        """Return string representation of sorted list."""
        return 'SortedList({0})'.format(list(self))

def ncr(n, r, p):

    num = den = 1
    for i in range(r):
        num = (num * (n - i)) % p
        den = (den * (i + 1)) % p
    return (num * pow(den,
                      p - 2, p)) % p


def sol(n):

    seti = set()
    for i in range(1,int(sqrt(n))+1):
        if n%i == 0:
            seti.add(n//i)
            seti.add(i)


    return seti
def lcm(a,b):

    return (a*b)//gcd(a,b)





#
# n,p = map(int,input().split())
#
# s = input()
#
# if n <=2:
#     if n == 1:
#         pass
#     if n == 2:
#         pass
# i = n-1
# idx = -1
# while i>=0:
#     z = ord(s[i])-96
#     k = chr(z+1+96)
#     flag = 1
#     if i-1>=0:
#         if s[i-1]!=k:
#             flag+=1
#     else:
#             flag+=1
#     if i-2>=0:
#         if s[i-2]!=k:
#             flag+=1
#     else:
#         flag+=1
#     if flag == 2:
#         idx = i
#         s[i] = k
#         break
# if idx == -1:
#     print('NO')
#     exit()
# for i in range(idx+1,n):
#     if
#

def moore_voting(l):

    count1 = 0
    count2 = 0
    first = 10**18
    second = 10**18
    n = len(l)
    for i in range(n):

        if l[i] == first:
            count1+=1
        elif l[i] == second:
            count2+=1

        elif count1 == 0:
            count1+=1
            first = l[i]

        elif count2 == 0:
            count2+=1
            second = l[i]
        else:
            count1-=1
            count2-=1

    for i in range(n):
        if l[i] == first:
            count1+=1
        elif l[i] == second:
            count2+=1
    if count1>n//3:
        return first
    if count2>n//3:
        return second

    return -1





def find_parent(u,parent):

    if u!=parent[u]:
        parent[u] = find_parent(parent[u],parent)

    return parent[u]






def dis_union(n):


    par = [i for i in range(n+1)]
    rank = [1]*(n+1)
    k = int(input())
    for i in range(k):
        a,b = map(int,input().split())
        z1,z2 = find_parent(a,par),find_parent(b,par)
        if z1!=z2:
            par[z1] = z2
            rank[z2]+=rank[z1]


def dijkstra(n,tot,hash):


    hea = [[0,n]]
    dis = [10**18]*(tot+1)
    dis[n] = 0
    boo = defaultdict(bool)
    check = defaultdict(int)
    while hea:
        a,b = heapq.heappop(hea)

        if boo[b]:
            continue

        boo[b] = True

        for i,w in hash[b]:
            if b == 1:
              c = 0
              if (1,i,w) in nodes:
                 c = nodes[(1,i,w)]
                 del nodes[(1,i,w)]

              if dis[b]+w<dis[i]:
                dis[i] = dis[b]+w

                check[i] = c

              elif dis[b]+w == dis[i] and c == 0:
                  dis[i] = dis[b]+w
                  check[i] = c

            else:

                if dis[b]+w<=dis[i]:
                    dis[i] = dis[b]+w
                    check[i] = check[b]



            heapq.heappush(hea,[dis[i],i])

    return check

def power(x,y,p):

    res = 1
    x = x%p
    if x == 0:
        return 0

    while y>0:

        if (y&1) == 1:
            res*=x

        x = x*x
        y = y>>1

    return res
#
# n,m = map(int,input().split())
# hash = defaultdict(list)
# ans = set()
# cur = 2
# rest = []
# now = []
# ba = []
# ho = defaultdict(bool)
# for i in range(m):
#     a,b = map(int,input().split())
#     ba.append(a)
#     if b == 1:
#         ans.add((a,1,cur))
#         now.append([a,1,cur])
#         ho[(1,cur)] = True
#         ho[(cur,1)] = True
#         cur+=1
#
#
#     else:
#         rest.append(a)
# ha = n-1
#
#
# rest.sort()
# # print(now)
# inf = -10**18
# i = 0
# cur = 2
# while ha!=m:
#     if rest == []:
#         break
#     yo = cur+1
#     while yo<=n:
#
#         x1,x2 =
#
#
#
# hash = defaultdict(list)
#
# for a,b,c in ans:
#     hash[a].append((b,c))
# yo = []
# for a in ba:
#     while hash[a]!=[]:
#         c,d = hash[a].pop(0)
#         yo.append((c,d))
#
# for a,b in yo:
#     print(a,b)







n,m = map(int,input().split())

ans = set()
cur = 2
rest = []
now = []
ba = []
hash = defaultdict(int)
for i in range(m):
    a,b = map(int,input().split())

    now.append([a,b,i])


now.sort()
yo = [[0,0]]*(m)

for i in range(m):
    a,b,x = now[i]
    ba.append([x,a])
    if b == 1:


        hash[(1,cur)] = a
        yo[x] = [1,cur]
        cur+=1


    else:
        rest.append(a)

rest.sort()
ba.sort()

ha = n-1
to = 2
fro = 3
while ha!=m:


        z = rest.pop(0)
        a,b = to,fro
        z1,z2 = hash[(1,to)],hash[(1,fro)]
        if z<z1 or z<z2:
            # print(z,a,b,z1,z2)
            print(-1)
            exit()
        ans.add((z,a,b))
        if rest == []:
            break
        to+=1
        if to == fro:
            fro+=1
            to = 2




hash = defaultdict(list)

for a,b,c in ans:
    hash[a].append((b,c))

# print(hash)
# print(ba)
for x,a in ba:

        if yo[x] == [0,0]:
         c,d = hash[a].pop(0)

         yo[x] = c,d


for a,b in yo:
    print(a,b)