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;
using ll=long long;
#define fr(i,n) for(ll i=0;i<(n);++i)
#define Fr(i,n) for(long long i=1;i<=(n);++i)
#define ifr(i,n) for(long long i=(n)-1;i>=0;--i)
#define iFr(i,n) for(long long i=(n);i>0;--i)
using Graph = vector<vector<int>>;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  ll a,ma,mi,maa,mii;
  ma=-10000000;
  mi=10000000;
  cin>>a;
  ll arr[a];
  fr(i,a){
    ll b;
    cin>>b;
    ma=max(b,ma);
    if(ma==b) maa=i+1;
    mi=min(b,mi);
    if(mi==b) mii=i+1;
    arr[i]=b;
  } 
  cout<<2*a-1<<"\n";
  if(ma+mi>0){
  fr(i,a){
    cout<<maa<<" "<<i+1<<"\n";
  }
  fr(i,a-1){
    cout<<i+1<<" "<<i+2<<"\n";
  }
  }
  if(ma+mi<=0){
  fr(i,a){
    cout<<mii<<" "<<i+1<<"\n";
  }
  ifr(i,a-1){
    cout<<i+2<<" "<<i+1<<"\n";
  }
  }
}