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 rep(i, n) for (int i = 0; i < n; i++)

int main() {
  int n;
  cin >> n;
  vector<ll> v(n);
  rep(i, n) cin >> v[i];
  int p = -1;
  ll ma = -1;
  rep(i, n) {
    if (ma < abs(v[i])) {
      ma = abs(v[i]);
      p = i;
    }
  }
  cout << 2*n - 1 << endl;
  rep(i, n) {
    cout << p+1 << ' ' << i+1 << endl;
  }
  rep(i, (n-1)) {
    int a, b;
    if (v[p] >= 0) {
      a = i+1;
      b = i+2;
    } else {
      a = n-i;
      b = a-1;
    }
    cout << a << ' ' << b << endl;
  }
}