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 = []
B=A[:]
B.sort()

if abs(B[0]) > abs(B[-1]) :
    absmax = B[0]
else :
    absmax = B[-1]

ind = A.index(absmax)

if absmax != 0 :
    fugou = absmax // abs(absmax)

    for i in range(n) :
        if A[i] * fugou < 0 :
            ANS.append([ind+1, i+1])

    if fugou == 1 :
        if ind+1 != 1 :
            ANS.append([ind+1, 1])
        for i in range(n-1) :
            ANS.append([i+1, i+2])
    else :
        if ind+1 != n :
            ANS.append([ind+1, n])
        for i in range(n,1,-1) :
            ANS.append([i, i-1])

    print(len(ANS))
    for i in range(len(ANS)) :
        print("{} {}".format(ANS[i][0], ANS[i][1]))
else :
    print(0)