from collections import defaultdict

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())


T,R=map(int,input().split())
t=0
N=5400
uf=UnionFind(N+1)
p=[-1]*(N+1)

s=set()
# スキル値, プレイヤーi, 出現チック
s.add((-10000000,-1,-1))
s.add((100000000,-1,-1))
pi=1

import bisect

while T<3600:
    L=list(map(int,input().split()))
    # nows=set()
    # nows.add((-10000000,-1,-1))
    # nows.add((100000000,-1,-1))
    t_ans=[]
    for i in range(L[0]):
        nowi=(L[i+1],pi,t)
        pi+=1
        sorteds=sorted(list(s))

        t=bisect.bisect_left(sorteds,nowi)

        used=False
        if abs(sorteds[t-1][0] - L[i+1])<5:
            sz=len(uf.members(pi))
            if sz<4:
                uf.union(pi,sorteds[t-1][1])
                t_ans.append(pi)
                used = True
                s.discard(sorteds[t-1])
        if abs(sorteds[t][0] - L[i+1])<5:
            sz=len(uf.members(pi))
            if sz<4:
                uf.union(pi,sorteds[t][1])
                t_ans.append(pi)
                used = True
                s.discard(sorteds[t])
        if used == False:
            s.add(nowi)
    ans4print=[]
    ans4print_num=0
    for ans in t_ans:
        m=uf.members(ans)
        mls=[]
        for i in range(1,len(m)) :
            mls.append([m[0],m[i]])
            ans4print_num+=1
        ans4print.append(mls)
    
    print(ans4print_num)
    for i in range (len(ans4print)):
        for e in ans4print[i]:
            print(*e)




        
        
        # for e in sorted[1:-2]:
        #     t=bisect.bisect_left(sortednows,e)
        #     ts,tp,tt = sortednows[t]
        #     if abs(sortednows[t-1][0] - ts) < 5:
        #         m.append()