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(int argc, const char *argv[]) {
  int n;
  cin >> n;

  vector<int> va(n);
  for (int i = 0; i < n; ++i) {
    cin >> va[i];
  }

  auto max_abs = [&]() {
    int max_a = va.front(), idx = 0;
    for (int i = 0; i < va.size(); ++i) {
      if (abs(max_a) < abs(va[i])) {
        max_a = va[i];
        idx = i;
      }
    }

    return idx;
  };

  int idx = max_abs();
  int max_a = va[idx];
  cout << (n - 1) * 2 << '\n';
  for (int i = 0; i < n; ++i) {
    if (idx != i) {
      cout << idx + 1 << ' ' << i + 1 << '\n';
    }
  }

  if (max_a >= 0) {
    for (int i = 0; i < n - 1; ++i) {
      cout << i + 1 << ' ' << i + 2 << '\n';
    }
  } else if (max_a < 0) {
    for (int i = n - 1; i > 0; --i) {
      cout << i + 1 << ' ' << i << '\n';
    }
  }
  return 0;
}