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 <cctype>
#include <algorithm>
#include <vector>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <utility>
#include <string>
#include <functional>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
typedef long long ll;
const int INF = 100000000, mod = 1000000007;
const ll LLINF = 1LL << 50;
using namespace std;



int main() {
    ll n, a[105], max = 0;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        if (abs(a[i]) > abs(a[max])) max = i;
    }
    
    cout << 2*n-2 << endl;
    for (int i = 1; i <= n; i++) {
        if (i == max+1) continue;
        else cout << max+1 << ' ' << i << endl;
    }
    if (a[max] >= 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;
}