T=[0,9,15,20,25,30,35,40,44,48,52,56,60,65,70,75,80,85,92,101]
Z=[0]*20
L=[0]*20
d=0
for t in range(int(input().split()[0])):
	N=map(int,input().split()[1:])
	a=[]
	for i in N:
		d+=1
		p=0
		while T[p]<=i:p+=1
		if Z[p]==0:L[p]=d
		else:a.append(str(L[p])+" "+str(d))
		Z[p]+=1
		if Z[p]>=4:Z[p]=0
	print(len(a))
	if len(a)>0:print("\n".join(a))