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 n;
int a[60];
int mx, mxid;

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        if (i == 1) {
            mx = a[i];
            mxid = 1;
        }
        else {
            if (abs(a[i]) > abs(mx)) {
                mx = a[i];
                mxid = i;
            }
        }
    }

    cout << 2*n - 2 << endl;
    for (int i = 1; i <= n; i++) {
        if (i == mxid) continue;
        cout << mxid << " " << i << endl;
        a[i] += mx;
    }

    if (mx > 0) {
        for (int i = 2; i <= n; i++) {
            cout << i-1 << " " << i << endl;
            a[i] += a[i-1];
        }
    } else {
        for (int i = n-1; i > 0; i--) {
            cout << i+1 << " " << i << endl;
            a[i] += a[i+1];
        }
    }

    return 0;
}