Problem:
Score : 600 points

Problem Statement

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.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include "bits/stdc++.h"
using namespace std;

int main() {
    int n;
    cin >> n;
    vector< int> v(n);
    int mni = 0, mxi = 0;
    for(int i = 0; i < n; ++i) {
        cin >> v[i];
        if(v[i] < v[mni]) mni = i;
        if(v[i] > v[mxi]) mxi = i;
    }

    cout << 2 * n - 1 << endl;

    if(abs(v[mxi]) >= abs(v[mni])) {
        for(int i = 0; i < n; ++i) {
            cout << mxi + 1 << ' ' << i + 1<< endl;
        }

        for(int i = 0; i < n - 1; i++) {
            cout << i + 1 << ' ' << i + 2 << endl;
        }
    }

    else {
        for(int i = 1; i <= n; ++i) {
            cout << mni + 1 << ' ' << i << endl;
        }

        for(int i = n; i > 1; i--) {
            cout << i << ' ' << i - 1 << endl;
        }
    }


}