#!/usr/bin/perl

open(FIL,"prob11data.txt");
@lines = <FIL>;
close(FIL);

#first, stuff the matrix
$h = $#lines;
@c = split(' ',$lines[0]);
$w = $#c;
@mat;
for ($i = 0; $i < $h; $i++) {
  @nums = split(' ',$lines[$i]);
  for ($j = 0; $j < $w; $j++) {
    $mat[$i][$j] = $nums[$j];
  }
}

$maxprod = 0;
for ($i = 0; $i < $h; $i++) {
  for ($j = 0; $j < $w - 4; $j++) {
    $n1 = $mat[$i][$j];
    $n2 = $mat[$i][$j+1];
    $n3 = $mat[$i][$j+2];
    $n4 = $mat[$i][$j+3];
    $prod = $n1 * $n2 * $n3 * $n4;
    if ($prod > $maxprod) {
      $maxprod = $prod;
    }
    if ($i < $h - 4) {
      $n2 = $mat[$i+1][$j+1];
      $n3 = $mat[$i+2][$j+2];
      $n4 = $mat[$i+3][$j+3];
    }
    $prod = $n1 * $n2 * $n3 * $n4;
    if ($prod > $maxprod) {
      $maxprod = $prod;
    }
    if ($i > 4) {
      $n2 = $mat[$i-1][$j+1];
      $n3 = $mat[$i-2][$j+2];
      $n4 = $mat[$i-3][$j+3];
    }
    $prod = $n1 * $n2 * $n3 * $n4;
    if ($prod > $maxprod) {
      $maxprod = $prod;
    }
  }
}

for ($i = 0; $i < $w; $i++) {
  for ($j = 0; $j < $h - 4; $j++) {
    $n1 = $mat[$j][$i];
    $n2 = $mat[$j][$i+1];
    $n3 = $mat[$j][$i+2];
    $n4 = $mat[$j][$i+3];
    $prod = $n1 * $n2 * $n3 * $n4;
    if ($prod > $maxprod) {
      $maxprod = $prod;
    }
    if ($i < $w - 4) {
      $n2 = $mat[$j+1][$i+1];
      $n3 = $mat[$j+2][$i+2];
      $n4 = $mat[$j+3][$i+3];
    }
    $prod = $n1 * $n2 * $n3 * $n4;
    if ($prod > $maxprod) {
      $maxprod = $prod;
    }
    if ($i > 4) {
      $n2 = $mat[$j-1][$i+1];
      $n3 = $mat[$j-2][$i+2];
      $n4 = $mat[$j-3][$i+3];
    }
    $prod = $n1 * $n2 * $n3 * $n4;
    if ($prod > $maxprod) {
      $maxprod = $prod;
    }
  }
}

print $maxprod . "\n";