import java.util.*;
import java.util.zip.*;
import java.util.List;
import java.util.regex.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*;
import java.util.function.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.table.*;
import java.io.*;
import java.net.*;
import java.lang.reflect.*;
import java.lang.ref.*;
import java.lang.management.*;
import java.security.*;
import java.security.spec.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.awt.geom.*;
import javax.imageio.*;
import java.math.*;
import java.time.Duration;
class main {

static double alphaChannelAverage(int[] pixels) {
  int n = pixels.length;
  long sum = 0;
  for (int i = 0; i < n; i++)
    sum += rgbAlpha(pixels[i]);
  return doubleRatio(sum, n);
}
static int rgbAlpha(int rgb) {
  return (rgb >> 24) & 0xFF;
}


static double doubleRatio(double x, double y) {
  return y == 0 ? 0 : x/y;
}





}