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 <algorithm>

using namespace std;
typedef long long lint;

void output(int a, int b) {
    cout << a << " " << b << endl;
}

int main() {
    int N;
    cin >> N;
    vector<int> A(N);
    int maxAbs = -1, index = -1;
    for (int i = 0; i < N; i++) {
        cin >> A[i];
        if (maxAbs < abs(A[i])) {
            index = i;
            maxAbs = abs(A[i]);
        }
    }
    cout << 2*N << endl;
    if (A[index] < 0) {
        output(index+1, index+1);
        output(index+1, N);
        output(N, N-1);
        for (int i = N-2; i >= 1; i--) {
            output(i+1, i+1);
            output(i+1, i);
        }
        output(1, 1);
    } else {
        output(index+1, index+1);
        output(index+1, 1);
        output(1, 2);
        for (int i = 1; i < N-1; i++) {
            output(i+1, i+1);
            output(i+1, i+2);
        }
        output(N, N);
    }
}