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 main():
    N = int(input())
    A = list(map(int, input().split()))
    r = []
    ma, mi = max(A), min(A)
    if ma * mi < 0:
        if abs(mi) > abs(ma):
            ma = mi
        mi = A.index(ma)
        for i, a in enumerate(A):
            if ma * a < 0:
                r.append((mi, i))
                A[i] += ma

    if min(A) >= 0:
        for i in range(1, N):
            if A[i] < A[i - 1]:
                A[i] += A[i - 1]
                r.append((i - 1, i))
    else:
        for i in reversed(range(N - 1)):
            if A[i] > A[i + 1]:
                A[i] += A[i + 1]
                r.append((i + 1, i))

    print(len(r))
    for rx, ry in r:
        print(rx + 1, ry + 1)

main()