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<cstdio>
#include<cmath>
#include<cctype>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<stack>
#include<string>
#define INF 0x3f3f3f3f
#define LC(a) (a<<1)
#define RC(a) (a<<1|1)
#define MID(a,b) ((a+b)>>1)
#define fin(name)  freopen(name,"r",stdin)
#define fout(name) freopen(name,"w",stdout)
#define CLR(arr,val) memset(arr,val,sizeof(arr))
#define FOR(i,start,end) for(int i=start;i<=end;i++)  
#define FAST_IO ios::sync_with_stdio(false);cin.tie(0);
using namespace std;
typedef long long LL;
const int N=5e4+5;
int a[N];

struct node1{
	int x,y;
}res[N];

int main(){
	int n,mi=1,ma=1;
	scanf("%d",&n);
	FOR(i,1,n){
		scanf("%d",&a[i]);
		if(a[i]>a[ma])
			ma=i;
		if(a[i]<a[mi])
			mi=i;
	}
	int i,cnt=0;
	if(abs(a[mi])>abs(a[ma])){
		i=1;
		while(i<n){
			if(a[i]<=a[i+1]){
				i++;
				continue;
			}
			res[++cnt].x=mi;
			res[cnt].y=i;
			a[i]+=a[mi];
			if(a[i]<a[mi])
				mi=i;
		}
	}
	else{
		i=n;
		while(i>1){
			if(a[i]>=a[i-1]){
				i--;
				continue;
			}
			res[++cnt].x=ma;
			res[cnt].y=i;
			a[i]+=a[ma];
			if(a[i]>a[ma])
				ma=i;
		}
	}
	printf("%d\n",cnt);
	if(cnt!=0){
		for(int i=1;i<=cnt;i++){
			printf("%d %d\n",res[i].x,res[i].y);
		}
	}
	return 0;
}