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;

int main() {
  long n,absmax=0,absmaxi=0;
  cin >> n;
  vector<long> a(n),ans1,ans2;
  for(long i=0;i<n;i++) cin >> a[i];
  
  for(long i=0;i<n;i++) {
    if(absmax<abs(a[i])) {
      absmax=abs(a[i]);
      absmaxi=i;
    }
  }
  for(long i=0;i<n;i++) {
    if(i==absmaxi) continue;
    ans1.push_back(absmaxi+1);
    ans2.push_back(i+1);
  }
  if(a[absmaxi]>0) {
    for(long i=0;i<n-1;i++) {
      ans1.push_back(i+1);
      ans2.push_back(i+2);
    }
  } else if(a[absmaxi]<0) {
    for(long i=n-2;i>=0;i--) {
      ans1.push_back(i+2);
      ans2.push_back(i+1);
    }
  }
  cout << ans1.size() << endl;
  for(long i=0;i<ans1.size();i++) cout << ans1[i] << " " << ans2[i] << endl;
}