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:
import sys

readline = sys.stdin.readline
MOD = 10 ** 9 + 7
INF = float('INF')
sys.setrecursionlimit(10 ** 5)


def main():
    n = int(readline())
    a = list(map(int, readline().split()))
    b = list(map(abs, a))
    idx = b.index(max(b))

    res = []
    for i, x in enumerate(a):
        a[i] += a[idx]
        res.append((idx + 1, i + 1))

    if a[idx] > 0:
        for i in range(1, n):
            if a[i - 1] > a[i]:
                a[i] += a[i - 1]
                res.append((i, i + 1))
    elif a[idx] < 0:
        for i in range(n - 2, -1, -1):
            if a[i] > a[i + 1]:
                a[i] += a[i + 1]
                res.append((i + 2, i + 1))

    print(len(res))
    for x, y in res:
        print(x, y)


if __name__ == '__main__':
    main()