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>
using namespace std;
#include<string.h>
#include<set>
#include<stdio.h>
#include<math.h>
#include<queue>
#include<map>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<cstring>
#include <cstdio>
#include <cstdlib>
#include<stack>
#include<vector>
int a[100];
int main()
{
    int n;
    cin>>n;
    int max1=-1e8;
    int t1,t2;
    for(int i=1; i<=n; i++)
    {
        cin>>a[i];
        if(max1<abs(a[i]))
        {
            max1=abs(a[i]);
            t1=i;
        }
    }
    cout<<2*n-1<<endl;
    for(int i=1;i<=n;i++)
        cout<<t1<<" "<<i<<endl;
    if(a[t1]>=0)
    {
        for(int i=2;i<=n;i++)
            cout<<i-1<<" "<<i<<endl;
    }
    else
    {
        for(int i=n-1;i>=1;i--)
            cout<<i+1<<" "<<i<<endl;
    }
    return 0;
}