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 <bits/stdc++.h>
#define INF 1e9
using namespace std;

int Abs(int n){
    if(n<0)return -n;
    else return n;
}

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin>>n;
    vector<int> a(n);
    for(int i=0;i<n;i++)cin>>a[i];
    int MAX=0,pos=0;
    for(int i=0;i<n;i++){
        if(Abs(MAX)<Abs(a[i])){
            MAX=a[i];
            pos=i;
        }
    }
    cout<<2*n-1<<endl;
    for(int i=0;i<n;i++)cout<<pos+1<<" "<<i+1<<endl;
    if(MAX>0){
        for(int i=0;i<n-1;i++)cout<<i+1<<" "<<i+2<<endl;
    }
    else{
        for(int i=n-2;i>=0;i--)cout<<i+2<<" "<<i+1<<endl;
    }

}