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 <string>
#include <algorithm>
#include <set>
#include <map>
#include <numeric>
#include <climits>
#include <math.h>
#include <memory.h>
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rrep(i, k, n) for(int i = (k); i < (int)(n); i++)
using namespace std;
using ll = long long;
int N, M;
int cnt = 0;
int ans = 0;
int tmp;
int main(){
    int N;
    cin >> N;
    int a[N];
    int maxindex = 0;
    int absmax = -1;
    rep(i, N) cin >> a[i];
    rep(i, N){
        if(abs(absmax) < abs(a[i])){
            absmax = a[i];
            maxindex = i;
        }
    }
    cout << 2 * N - 1 << endl;
    rep(i, N) cout << maxindex + 1 << " " << i + 1 << endl;
    rep(i, N - 1){
        if(absmax < 0) cout << N - i << " " << N - i - 1 << endl;
        else cout << i + 1 << " " << i + 2 << endl;
    }
    return 0;
}