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:
import sys
input = sys.stdin.buffer.readline

def main():
    N = int(input())
    A = list(map(int,input().split()))
    a,b = max(A), min(A)
    ap,bp = A.index(a),A.index(b)
    ans = []
    if a >= -b:
        for i in range(N):
            if A[i] < 0:
                A[i] += a
                ans.append([ap+1,i+1])
        for i in range(N-1):
            A[i+1] += A[i]
            ans.append([i+1,i+2])
    else:
        for i in range(N):
            if A[i] > 0:
                A[i] += b
                ans.append([bp+1,i+1])
        for i in range(N-1):
            A[-i-2] += A[-i-1]
            ans.append([N-i,N-i-1])
            
    L = len(ans)
    print(L)
    for i in range(L):
        print(*ans[i])
        
if __name__ == "__main__":
    main()