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<cstdio>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<queue>
#include<vector>
#include <bitset>
#include<math.h>
#include<map>
#include<set>
#include <climits>
using namespace std;
#define INF 1100000
#define MOD 1000000007
typedef long long ll;
typedef pair<int,int> P;



int main(){
    vector<P> ans;
    int N;
    cin>>N;
    ll a[60],temp=0,x;
    for(int i=0;i<N;i++){
        cin>>a[i];
        if(abs(a[i])>temp){
            temp=abs(a[i]);
            x=i;
        }
    }
    cout<<(N-1)+(N-1)<<endl;
    for(int i=0;i<N;i++){
        if(i==x) continue;
        cout<<x+1<<" "<<i+1<<endl;
    }
    if(a[x]<0){
        for(int i=N;i>=2;i--) cout<<i<<" "<<i-1<<endl;
    }else{
        for(int i=1;i<=N-1;i++) cout<<i<<" "<<i+1<<endl;
    }

}