Problem:
Score : 600 points

Problem Statement

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.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in Python (3.4.3) (judge verdict: Wrong Answer)

n = int(input())
a = list(map(int, input().split()))

k = 0
if max(a) == min(a):
    print(0)
    exit()
elif max(a) + min(a) == 0:
    print(-1)
    exit()
elif max(a) * min(a) < 0:
    print((n - 1) * 2)
    if max(a) + min(a) >= 0:
        k = a.index(max(a)) + 1
    else:
        k = a.index(min(a)) + 1
    for i in range(1, n + 1):
        if i != k:
            print(k, i)
else:
    print(n - 1)
    if max(a) > 0:
        k = a.index(max(a)) + 1
    else:
        k = a.index(min(a)) + 1

if a[k - 1] > 0:
    for i in range(1, n):
        print(i, i + 1)
else:
    for i in range(n, 1, -1):
        print(i, i - 1)