Problem: Snuke has an integer sequence, a, of length N. The i-th element of a (1-indexed) is a_{i}.

He can perform the following operation any number of times:

* Operation: Choose integers x and y between 1 and N (inclusive), and add a_x to a_y.



He would like to perform this operation between 0 and 2N times (inclusive) so that a satisfies the condition below. Show one such sequence of operations. It can be proved that such a sequence of operations always exists under the constraints in this problem.

* Condition: a_1 \leq a_2 \leq ... \leq a_{N}

Constraints

* 2 \leq N \leq 50
* -10^{6} \leq a_i \leq 10^{6}
* All input values are integers.

Input

Input is given from Standard Input in the following format:


N
a_1 a_2 ... a_{N}


Output

Let m be the number of operations in your solution. In the first line, print m. In the i-th of the subsequent m lines, print the numbers x and y chosen in the i-th operation, with a space in between. The output will be considered correct if m is between 0 and 2N (inclusive) and a satisfies the condition after the m operations.

Examples

Input

3
-2 5 -1


Output

2
2 3
3 3


Input

2
-1 -3


Output

1
2 1


Input

5
0 0 0 0 0


Output

0

Solution (in PYTHON3):

Solution:
def d_non_decreasing(N, A):
    a_max = max(A)
    a_argmax = A.index(a_max) + 1
    a_min = min(A)
    a_argmin = A.index(a_min) + 1  # +1するのは問題の数列が1-indexedだから

    if abs(a_max) >= abs(a_min):
        plus_index = a_argmax
        cumsum_range = range(1, N)
        cumsum_direction = +1
    else:
        plus_index = a_argmin
        cumsum_range = range(N, 1, -1)
        cumsum_direction = -1

    ans = [str(2 * N - 1)]  # 2N-1回の操作でソートされた数列になる
    for k in range(1, N + 1):
        ans.append('{} {}'.format(plus_index, k))  # 各要素に一律に加算
    for k in cumsum_range:
        ans.append('{} {}'.format(k, k + cumsum_direction))  # 累積和を取る
    ans = '\n'.join(ans)
    return ans
  
N = int(input())
A = [int(i) for i in input().split()]
print(d_non_decreasing(N, A))