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:
def solve1():
    for i in range(N-1):
        ans.append((i+1,i+2))
        A[i+1]+=A[i]
def solve2():
    for i in reversed(range(1,N)):
        ans.append((i+1,i))
        A[i-1]+=A[i]

N=int(input())
A=list(map(int,input().split()))
l=min(A);r=max(A)
wl=A.index(l);wr=A.index(r)

ans=[]
if l>=0:
    solve1()
elif r<0:
    solve2()
else:
    if abs(l)>abs(r):
        for i in range(N):
            if A[i]>0:
                ans.append((wl+1,i+1))
                A[i]+=l
        solve2()
    else:
        for i in range(N):
            if A[i]<0:
                ans.append((wr+1,i+1))
                A[i]+=r
        solve1()
print(len(ans))
for x,y in ans:
    print(x,y)