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: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb push_back
#define fi first
#define se second
typedef pair<ll,ll> P;
#define Mod 1000000007
using VP = vector<P>; using VVP = vector<VP>;
using VI = vector<ll>; using VVI = vector<VI>; using VVVI = vector<VVI>;
#define INF 1ll<<59

int main(){
  ll i,j;
  ll n;
  cin>>n;
  ll a[n];
  for(i=0;i<n;i++) cin>>a[i];
  
  ll m=0;
  ll f;
  for(i=0;i<n;i++){
    m=max(abs(a[i]),m);
    if(m==a[i]) f=i;
    if(m==-a[i]) f=-i;
  }

  vector<P> v;

  if(f>=0){
    for(i=1;i<n;i++){
        v.pb(P(f,i));
        v.pb(P(f,i));
        f=i;
    }
  }
  else {
    f=-f;
    for(i=n-2;i>=0;i--){
      v.pb(P(f,i));
      v.pb(P(f,i));
      f=i;
    }
  }
  
  cout<<v.size()<<endl;
  for(i=0;i<v.size();i++) cout<<1+v[i].fi<<" "<<1+v[i].se<<endl;
  return 0;
}