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;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000


int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    int a[N];
    rep(i, N) cin >> a[i];

    int max = abs(a[0]);
    int index = 0;
    rep(i, N-1) {
        if (max < abs(a[i+1])) {
            max = abs(a[i+1]);
            index = i+1;
        }
    }
    cout << N*2-1 << endl;
    rep(i, N) cout << index+1 << " " << i+1 << endl;
    if(a[index] < 0) {
        for(int i = N; i > 1; i--) {
            cout << i << " " << i-1 << endl;
        }
    } else {
        rep(i, N-1) {
            cout << i+1 << " " << i+2 << endl;
        }        
    }



    return 0;
}