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 <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <cstring>
#define rep(i, N) for (int i = 0; i < (int)N; i++)
using namespace std;
typedef long long ll;
const ll LLINF = 9223372036854775807;
const int MOD = 1000000007;

int main() {
  int N; cin >> N;
  int a[N]; rep(i, N) cin >> a[i];

  int max_abs = 0;
  rep(i, N) if (abs(a[max_abs]) < abs(a[i])) max_abs = i;

  cout << 2*N-1 << endl;
  rep(i, N) cout << max_abs+1 << " " << i+1 << endl;
  if (a[max_abs] < 0) for(int i=N; i>1; i--) cout << i << " " << i-1 << endl;
  else for(int i=1; i<N; i++) cout << i << " " << i+1 << endl;
  return 0;
}