# Step 1. 入力
N = int(input())
A = [ 0 ] * N
for i in range(N):
    A[i] = int(input())

# Step 2. 貪欲法
Target = 5 * (10 ** 99)
Answer = []
for i in range(1, N):
    avg = (A[0] + A[i]) // 2
    if abs(Target - avg) < abs(Target - A[0]):
        A[0] = avg
        A[i] = avg
        Answer.append([0, i])

# Step 3. 答えを出力
print(len(Answer))
for i in Answer:
    print(str(i[0] + 1) + " " + str(i[1] + 1))