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;
typedef long long ll;

int main(){
    int n,max_a = -1,max_i = -1;
    cin >> n;
    vector<int> a(n);
    bool is_p = 0,is_n = 0;

    for(int i = 0;i < n;i ++){
        cin >> a[i];

        if(a[i]>=0) is_p = 1;
        else is_n = 1;
        
        if(max_a<abs(a[i])) {max_a = abs(a[i]);max_i = i;}
    }
    if(a[max_i]>=0) is_n = 0;
    else is_p = 0;

    cout << 2*(n-1) << endl;
    for(int i = 0;i < n;i ++){
        if(max_i!=i) cout << max_i+1 << " " << i+1 << endl;
    }
    if(is_p) for(int i = 0;i < n-1;i ++){
        cout << i+1 << " " << i+2 << endl;
    }
    else for (int i = n-1;i >= 1;i --){
        cout << i+1 << " " << i << endl;
    }

    return 0;
}