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, *A = map(int, open(0).read().split())

v_max = max(A)
v_min = min(A)

flg1 = v_max > 0 and v_min >= 0
flg2 = v_max <= 0 and v_min <= 0
flg3 = v_max * v_min < 0 and abs(v_max) >= abs(v_min)
flg4 = v_max * v_min < 0 and abs(v_max) < abs(v_min)

s = sorted([(i + 1, v) for i, v in enumerate(A)], key=lambda x: x[1])
ans = []
if flg1 or flg3:
    if flg3:
        i_max = s[-1][0]
        for j in range(1, N + 1):
            ans.append((i_max, j))
            
    for j in range(1, N):
        ans.append((j, j + 1))
else:
    if flg4:
        i_min = s[0][0]
        for j in range(1, N + 1):
            ans.append((i_min, j))
            
    for j in reversed(range(1, N)):
        ans.append((j + 1, j))
        
print(len(ans))
for v in ans:
    print(*v)