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:
#!/usr/bin/env python3

def main():
    N = int(input())
    a = [int(s) for s in input().split(' ')]

    result = []

    max_a = max(a)
    min_a = min(a)

    if 0 <= max_a + min_a:
        k = a.index(max_a)
        sk = str(k + 1) + ' '
        for i in range(N):
            if a[i] < 0:
                result.append(sk + str(i + 1))
        for i in range(1, N):
            result.append(str(i) + ' ' + str(i + 1))
    else:
        k = a.index(min_a)
        sk = str(k + 1) + ' '
        for i in range(N):
            if a[i] > 0:
                result.append(sk + str(i + 1))
        for i in range(N - 1, 0, -1):
            result.append(str(i + 1) + ' ' + str(i))

    print(len(result))
    for s in result:
        print(s)

if __name__ == '__main__':
    main()