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 PYTHON):

Solution:
n = input()
num = map(int, raw_input().split())
ma = max(num)
mi = min(num)
l = list()
if ma*mi < 0:
    if ma > abs(mi):
        index = num.index(ma)
    else:
        index = num.index(mi)
    for i in xrange(n):
        l.append("%d %d" % (index+1, i+1))
    b = num[index]
else:
    b = 0
    for i in num:
        if i:
            b = i
            break

if b == 0:
    pass
elif b < 0:
    for i in xrange(n-1, 0, -1):
        l.append("%d %d" % (i+1, i))
else:
    for i in xrange(0, n-1):
        l.append("%d %d" % (i+1, i+2))

print len(l)
for i in l:
    print i