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 <cstdio>
#include <algorithm>
#include <vector>
#include <cstdlib>
using namespace std;


int n;
int a[55];
vector<pair<int,int>> v;
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&a[i]);
    }

    int mx = -1;
    int idx;
    for(int i=1;i<=n;i++){
        if (abs(a[i]) > mx){
            idx = i;
            mx = abs(a[i]);
        }
    }
    for(int i=1;i<=n;i++){
        if(i!=idx){
            v.emplace_back(idx,i);
        }
    }
    if(a[idx] > 0){
        for(int i=2;i<=n;i++){
            v.emplace_back(i-1,i);
        }
    }
    else {
        for(int i=n-1;i>=1;i--){
            v.emplace_back(i+1,i);
        }

    }

    printf("%d\n", int(v.size()));
    for(auto p : v){
        printf("%d %d\n", p.first, p.second);
    }
}