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>
using namespace std;

int main(){
    int n; cin>>n;
    vector<int> a(n);

    int mx = 0,ind;

    for(int i=0; i<n; i++){
        cin>>a[i];
        if(abs(a[i])>=abs(mx)){
            mx = a[i];
            ind = i;
        }
    }

    ind++;

    vector<pair<int,int>> pairs;

    for(int i=1; i<=n; i++){
        pairs.push_back(make_pair(ind,i));
    }

   if(mx >= 0){
        for(int i=1; i<n; i++){
            pairs.push_back(make_pair(i,i+1));
        }
    }

    else{
        for(int i=n; i>1; i--){
            pairs.push_back(make_pair(i,i-1));
        }
    }

    cout<<pairs.size()<<endl;

    for(int i=0; i<pairs.size(); i++){
        cout<<pairs[i].first<<" "<<pairs[i].second<<endl;
    }

    return 0;      
}