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,n) for (int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

int main() {
    int N; cin >> N;
    vector<int> a(N);
    int big = 0;
    int bignum = -1;
    rep(i, N){
        cin >> a[i];
        if(abs(a[i]) > abs(big)){
            big = a[i];
            bignum = i;
        }
    }

    if(bignum == -1){
        cout << 0 << endl;
        return 0;
    }

    cout << 2 * N - 1 << endl;
    for (int i = 1; i <= N; i++){
        cout << bignum+1 << " " << i << endl;
    }

    if(big > 0){
        for (int i = 1; i < N; i++){
            cout << i << " " << i+1 << endl;
        }
    } else {
        for (int i = N; i > 1; i--){
            cout << i << " " << i-1 << endl;
        }
    }

    return 0;
}