from heapq import *


def rec():
    ret = int(input())
    if ret == -1:
        exit()

def out():
    global g
    maxa = max(A)
    g2 = g ^ maxa
    if maxa <= g2:
        i = A.index(max)
        print(i + 1, g2)
    else:
        g2 = g ^ maxa
        for i in range(n):
            if A[i] >= g2:
                break
        g ^= A[i]
        A[i] = g
        g ^= g

def inp():
    global g
    i, k = map(int, input().split())
    g ^= A[i - 1]
    A[i - 1] -= k
    g ^= A[i - 1]


n = int(input())
A = list(map(int, input().split()))
g = 0
q = []
for i, a in enumerate(A):
    g ^= a
    q.append((-a, i))

if g == 0:
    print(0)
else:
    print(1)

heapify(q)

while 1:
    tmpa = []
    while g != 0:
        x,i = heappop(q)
        gtmp = g ^ A[i]
        if gtmp < A[i]:
            subt = A[i] - gtmp
            A[i] = gtmp
            g = 0
            print(i + 1,subt)
            rec()
            if gtmp > 0:
                tmpa.append((gtmp,i))
        else:
            tmpa.append((x,i))

    for xx in tmpa:
        heappush(q,xx)

    inp()
    rec()