t,r = map(int,input().split())
p = 1
for _ in range(t):
    n,*S = map(int,input().split())
    L = []
    stack = []
    for s,i in sorted([(s,i) for i,s in enumerate(S,p)]):
        if (stack and abs(stack[0][1]-s) >= 15) or len(stack) == r:
            for j in range(len(stack)-1):
                L.append((stack[j][0],stack[j+1][0]))
            stack.clear()
        stack.append((i,s))
    for j in range(len(stack)-1):
        L.append((stack[j][0],stack[j+1][0]))
    print(len(L),flush=True)
    for u,v in L:
        print(u,v,flush=True)
    p += n