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 JAVA):

Solution:
import java.util.*;


public class Main {
    static void solve() {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        ArrayList<Integer> a = new ArrayList<>();
        int min = 0;
        int max = 0;
        int minIndex = 0;
        int maxIndex = 0;
        for(int i = 0; i < n; i++){
            int na = sc.nextInt();
            if (na < min) {
                min = na;
                minIndex = i;
            }else if(na > max) {
                max = na;
                maxIndex = i;
            }
            a.add(na);
        }
        ArrayList<String> ans = new ArrayList<>();

        if(Math.abs(max) > Math.abs(min)){
            for(int i = 0; i < n; i++){
                if(a.get(i) < 0){
                    ans.add(String.valueOf(maxIndex+1) + " " + String.valueOf(i+1));
                }
            }
            for(int i = 0; i < n-1; i++){
                ans.add(String.valueOf(i+1) + " " + String.valueOf(i+2));
            }
        }else{
            for(int i = 0; i < n; i++){
                if(a.get(i) > 0){
                    ans.add(String.valueOf(minIndex+1) + " " + String.valueOf(i+1));
                }
            }
            for(int i = n-1; i >= 1; i--){
                ans.add(String.valueOf(i+1) + " " + String.valueOf(i));
            }
        }

        System.out.println(ans.size());
        for(String s : ans){
            System.out.println(s);
        }
    }

    public static void main(String[] args) {
        solve();
    }
}