class Exercise3
{
  // returns maximum element in array a 
  // of non-negative integers (-1, if a is empty)
  public static int maximum(int[] a) 
  {
    int n = a.length;
    if (n == 0) 
      return -1;
    else 
    {
      int m = -1;
      for (int i = 0; i < n; i++)
      {
        if (a[i] > m) m = a[i];
      }
      return m;
    }
  }
}