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

def inp():
    global g
    i, k = map(int, input().split())
    i -= 1
    g ^= A[i]
    dic[A[i]].remove(i)
    A[i] -= k
    if A[i] == 0:
        remain.remove(i)
    else:
        dic[A[i]].add(i)
    g ^= A[i]

def find(x):
    j = 0
    if len(dic[x]) > 0:
        return next(iter(dic[x]))
    else:
        return -1

from collections import defaultdict
dic = defaultdict(set)
n = int(input())
A = list(map(int, input().split()))
remain = set(range(n))
g = 0
for i, a in enumerate(A):
    g ^= a
    dic[a].add(i)

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

while 1:
    #print(A,g)
    if g != 0:
        i = find(g)
        if i == -1:
            for j in remain:
                gt = A[j] ^ g
                if gt <= A[j]:
                    i = j
                    break
        dic[A[i]].remove(i)
        to = A[i] ^ g
        subt = A[i] - to
        A[i] = to
        if A[i] == 0:
            remain.remove(i)
        else:
            dic[A[i]].add(i)
        g = 0
        print(i + 1, subt)
        rec()

    #if sum(A) == 0:
    #    print("finish")
    #    exit()
    #print(A,g)
    inp()
    rec()