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 JAVA):

Solution:
import java.io.*;
import java.util.*;
 
 
public class Main implements Runnable {
 
  public void run() {
    BetterScanner scanner = new BetterScanner(System.in);
  
    int n = scanner.nextInt();
    int[] aa = new int[n];
    for (int i = 0 ; i < n ; i ++) {
      aa[i] = scanner.nextInt();
    }

    int posMax = 0;
    int posPos = 0;
    int negMax = 0;
    int negPos = 0;
    for (int i = 0 ; i < n ; i ++) {
      if (aa[i] >= 0 && aa[i] >= posMax) {
        posMax = aa[i];
        posPos = i;
      }
      if (aa[i] <= 0 && aa[i] <= negMax) {
        negMax = aa[i];
        negPos = i;
      }
    }

    int op = 0;
    StringBuilder output = new StringBuilder();
    if (posMax >= -negMax) {
      for (int i = 0 ; i < n ; i ++) {
        if (aa[i] < 0) {
          output.append(posPos + 1).append(" ").append(i + 1).append("\n");
          op ++;
        }
      }
      for (int i = 0 ; i <= n - 2 ; i ++) {
        output.append(i + 1).append(" ").append(i + 2).append("\n");
        op ++;
      }
    } else {
      for (int i = 0 ; i < n ; i ++) {
        if (aa[i] > 0) {
          output.append(negPos + 1).append(" ").append(i + 1).append("\n");
          op ++;
        }
      }
      for (int i = n - 1 ; i >= 1 ; i --) {
        output.append(i + 1).append(" ").append(i).append("\n");
        op ++;
      }
    }
    System.out.println(op);
    System.out.println(output);
  }
 
  public static void main(String[] args) {
    Main main = new Main();
    main.run();
  }
 
  // scanner slightly faster than usual ones
  public static class BetterScanner {
 
    private InputStream stream;
    private byte[] buffer = new byte[1024];
    private int pointer = 0;
    private int bufferLength = 0;
 
    public BetterScanner(InputStream stream) {
      this.stream = stream;
    }
 
    private boolean updateBuffer() {
      if (pointer >= bufferLength) {
        pointer = 0;
        try {
          bufferLength = stream.read(buffer);
        } catch (IOException exception) {
          exception.printStackTrace();
        }
        return bufferLength > 0;
      } else {
        return true;
      }
    }
 
    private int read() {
      if (updateBuffer()) {
        return buffer[pointer ++];
      } else {
        return -1;
      }
    }
 
    public boolean hasNext() {
      skipUnprintable();
      return updateBuffer();
    }
 
    private void skipUnprintable() { 
      while (updateBuffer() && !isPrintableChar(buffer[pointer])) {
        pointer ++;
      }
    }
 
    public String next() {
      if (hasNext()) {
        StringBuilder builder = new StringBuilder();
        int codePoint = read();
        while (isPrintableChar(codePoint)) {
          builder.appendCodePoint(codePoint);
          codePoint = read();
        }
        return builder.toString();
      } else {
        throw new NoSuchElementException();
      }
    }
 
    public long nextLong() {
      if (hasNext()) {
        long number = 0;
        boolean minus = false;
        int codePoint = read();
        if (codePoint == '-') {
          minus = true;
          codePoint = read();
        }
        if (codePoint >= '0' && codePoint <= '9') {
          while (true) {
            if (codePoint >= '0' && codePoint <= '9') {
              number *= 10;
              number += codePoint - '0';
            } else if (codePoint < 0 || !isPrintableChar(codePoint)) {
              return (minus) ? -number : number;
            } else {
              throw new NumberFormatException();
            }
            codePoint = read();
          }
        } else {
          throw new NumberFormatException();
        }
      } else {
        throw new NoSuchElementException();
      }
    }
 
    public int nextInt() {
      long number = nextLong();
      if (number >= Integer.MIN_VALUE && number <= Integer.MAX_VALUE) {
        return (int)number;
      } else {
        throw new NumberFormatException();
      }
    }
 
    private boolean isPrintableChar(int codePoint) {
      return codePoint >= 33 && codePoint <= 126;
    }
 
  }
 
}