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, = map(int, input().split())
minv = min(A)
maxv = max(A)
mini = A.index(minv)
maxi = A.index(maxv)

ans = []


def op(x, y):
    A[y] += A[x]
    ans.append([x, y])


if minv < 0 and maxv > 0:
    if abs(minv) <= maxv:
        for i in range(N):
            if A[i] < 0:
                op(maxi, i)
    else:
        for i in range(N):
            if A[i] > 0:
                op(mini, i)

minv = min(A)
maxv = max(A)
mini = A.index(minv)
maxi = A.index(maxv)

if maxv <= 0:
    op(mini, N-1)
    for i in range(N-2, -1, -1):
        op(i+1, i)
else:
    op(maxi, 0)
    for i in range(1, N):
        op(i-1, i)

print(len(ans))
for x, y in ans:
    print(x+1, y+1)