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

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

def remX(x, i):
    j = 0
    while x > 0:
        if x & 1:
            X[j].remove(i)
        x >>= 1
        j += 1

def setX(x, i):
    j = 0
    while x > 0:
        if x & 1:
            X[j].add(i)
        x >>= 1
        j += 1

def find(x):
    j = 0
    tmp = set(range(n))
    while x > 0:
        if x & 1:
            tmp &= X[j]
        j += 1
        x >>= 1
    if tmp:
        return next(iter(tmp))
    else:
        return -1

X = [set() for _ in range(14)]
n = int(input())
A = list(map(int, input().split()))
g = 0

for i, a in enumerate(A):
    g ^= a
    setX(a, i)

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

while 1:
    if g != 0:
        i = find(g)
        if i == -1:
            maxa = max(A)
            i = A.index(maxa)

        remX(A[i], i)
        to = A[i] ^ g
        subt = A[i] - to
        A[i] = to
        setX(to, i)
        g = 0
        print(i + 1, subt)
        rec()

    inp()
    rec()