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
n = int(input())
INF = 10**18
a_ls = [int(i) for i in sys.stdin.readline().split()]
max_ind = 1
_max = a_ls[0]
min_ind = 1
_min = a_ls[0]

for i, a in enumerate(a_ls, 1):
    if a > _max:
        _max = a
        max_ind = i
    if a < _min:
        _min = a
        min_ind = i


flg = abs(_max) >= abs(_min)
ls = []
if flg:
    for i in range(1,n+1):
        if i != max_ind:
            ls.append((max_ind, i))
    for i in range(1,n):
        ls.append((i, i+1))
else:
    for i in range(1, n + 1):
        if i != min_ind:
            ls.append((min_ind, i))
    for i in range(n, 1, -1):
        ls.append((i, i - 1))
print(len(ls))
for x, y in ls:
    print(x, y)