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;
typedef long long ll;
typedef pair <int,int> pa;
const int N = 2e5+100;

int n;
int a[N];
void solve()
{
   cin>>n;
   int z=0,pos=1;
   for(int i=1;i<=n;i++) {
    cin>>a[i];
    if(abs(a[i])>abs(z)) z=a[i],pos=i;
   }
   if(z<0) {
      cout<<2*n<<endl;
      cout<<pos<<" "<<1<<endl;
      cout<<pos<<" "<<1<<endl;
      for(int i=n;i>=2;i--) {
         cout<<1<<" "<<i<<endl;
         cout<<1<<" "<<1<<endl;
      }
   }
   else if(z>0) {
     cout<<2*n<<endl;
     cout<<pos<<" "<<n<<endl;
     cout<<pos<<" "<<n<<endl;
     for(int i=1;i<n;i++) {
        cout<<n<<" "<<i<<endl;
        cout<<n<<" "<<n<<endl;
     }
   }
   else cout<<0<<endl;
}
int main()
{
    ios::sync_with_stdio(0);cin.tie(0);
    solve();
    return 0;
}