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:
N = int(input())
a = list(map(int, input().split()))
ans = []
for i in range(N-1):
    if a[i] > a[i+1] >= 0:
        a[i+1] += a[i]
        ans.append((i+1, i+2))
    if a[i] >= 0 > a[i+1] and a[i] + a[i+1] >= 0:
        a[i+1] += a[i] * 2
        ans.append((i+1, i+2))
        ans.append((i+1, i+2))
for i in range(N-1)[::-1]:
    if 0 >= a[i] > a[i+1]:
        a[i] += a[i+1]
        ans.append((i+2, i+1))
    if a[i] >= 0 > a[i+1]:
        a[i] += a[i+1] * 2
        ans.append((i+2, i+1))
        ans.append((i+2, i+1))
print(len(ans))
for x, y in ans:
    print(x, y)