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>
#define rep(i, a, n) for(int i = a; i < n; i++)
using namespace std;
typedef pair<int, int> P;

int main(){
	int n;
	cin >> n;
	vector<int> a(n);
	int MAX = 0, idx = 0;
	rep(i, 0, n){
		cin >> a[i];
		if(abs(a[i]) > MAX){
			MAX = abs(a[i]);
			idx = i;
		}
	}
	vector<P> ans;
	rep(i, 0, n){
		ans.push_back({idx + 1, i + 1});
	}
	if(a[idx] >= 0){
		rep(i, 0, n - 1){
			ans.push_back({i + 1, i + 2});
		}
	}else{
		for(int i = n - 1; i >= 1; i--){
			ans.push_back({i + 1, i});
		}
	}
	cout << ans.size() << endl;
	for(int ii = 0; ii < ans.size(); ii++){
		cout << ans[ii].first << " " << ans[ii].second << endl;
	}
}