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 CPP):

Solution:
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<map>
using namespace std;
const int maxn = 55;
int x[maxn];
int n;
map<int,int> Q;
int main()
{
    cin>>n;
    int sum = 0;
    int max1 = -1e6-5;
    int min1 = 1e6+5;
    int now = 0;
    for(int i=1;i<=n;i++)
    {
        cin>>x[i];
        Q[x[i]]=i;
        max1 = max(max1,x[i]);
        min1 = min(min1,x[i]);
    }
    if(abs(min1)>abs(max1))now = 1;
    if(min1<=0&&max1>=0)
    {
        cout<<2*n-1<<endl;
        for(int i=1;i<=n;i++)
        {
            if(now)cout<<Q[min1]<<" "<<i<<endl;
            else cout<<Q[max1]<<" "<<i<<endl;
        }
    }
    else cout<<n-1<<endl;
    if(now)
    {
        for(int i=n;i>1;i--)
        {
            cout<<i<<" "<<i-1<<endl;
        }
    }
    else
    {
        for(int i=2;i<=n;i++)
        {
            cout<<i-1<<" "<<i<<endl;
        }
    }
    return 0;
}