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 <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
#define N_max 50

int main(){
    int N;
    cin >>N;
    int A[N_max];
    int abs_max=0,abs_ind=0;
    for(int i=0;i<N;i++){
        cin >> A[i];
        if(abs_max < abs(A[i])){
            abs_max=abs(A[i]);
            abs_ind=i;
        }
    }
    cout << 2*N-2 <<endl;
    for(int i=0;i<N;i++){
        if(i!=abs_ind) cout << abs_ind+1 << " " << i+1 << endl;
    }
    if(A[abs_ind] >=0){
        for(int i=1;i<N;i++) cout << i << " " << i+1 <<endl;
    }
    else{
        for(int i=N; 1< i ;i--) cout << i << " " <<i-1 <<endl;
    }
}