Problem:
Score : 600 points

Problem Statement

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.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>
#include <vector>
#include <queue>
#include <cmath>
#include <cstring>
using namespace std; 
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
#define ll long long
#define pb push_back
const ll mod=1e9+7;
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define rep2(i,a,b) for(int i=a;i>=b;i--)
int a[55];
int main(int argc, char** argv) {
	int n;
	cin>>n;
	int fgz=0,fgf=0,mx=0,mn=0,bg,sm;
	rep(i,1,n)
	scanf("%d",&a[i]);
	rep(i,1,n)
	{
		if(a[i]>0)fgz=1;
		if(a[i]<0)fgf=1;
		if(a[i]>=mx)bg=i;
		mx=max(mx,a[i]);
		if(a[i]<=mn)sm=i;
		mn=min(mn,a[i]);
	}
	if(!fgf&&!fgz)
	{
		cout<<0;
	}
	vector<pair<int,int> >ans;
	if(!fgz&&fgf)
	{
		printf("%d\n",n-1);
		rep2(i,n-1,1)
		{
			printf("%d %d\n",i+1,i);
		}
	}
	if(fgz&&!fgf)
	{
		printf("%d\n",&n-1);
		rep(i,2,n)
		{
			printf("%d %d\n",i-1,i);
		}
	}
	if(fgz&&fgf)
	{
		if(abs(mx)>=abs(mn))
		{
			rep(i,1,n)
			{
				if(i==bg)continue;
				ans.pb({i,bg});
			}
			rep(i,2,n)
			{
				ans.pb({i,i-1});
			}
			cout<<ans.size()<<endl;
			rep(i,0,ans.size()-1)cout<<ans[i].second<<" "<<ans[i].first<<endl;
		}
		if(abs(mx)<abs(mn))
		{
			rep(i,1,n)
			{
				if(i==sm)continue;
				ans.pb({i,sm});
			}
			rep2(i,n-1,1)
			{
				ans.pb({i,i+1});
			}
			cout<<ans.size()<<endl;
			rep(i,0,ans.size()-1)cout<<ans[i].second<<" "<<ans[i].first<<endl;
		}
	}
	return 0;
}