var num=0;

imgArray = [
  ['../images/liberationday/2139.jpg','photo',''],
  ['../images/liberationday/18603.jpg','photo',''],
  ['../images/liberationday/a032.jpg','photo', ''],
  ['../images/liberationday/decom_02.jpg','photo', ''],
  ['../images/liberationday/decom_05.jpg','photo',''],
  ['../images/liberationday/guam.jpg','photo',''],
  ['../images/liberationday/Memorial.jpg','photo',''],
  ['../images/liberationday/USMC-C-Guam-OFC.jpg','photo',''],
  ['../images/liberationday/USMC-C-Guam-p37.jpg','photo','']
]

function slideshow(slide_num) {
  document.getElementById('mypic').src=imgArray[slide_num][0];
  document.getElementById('mypic').alt=imgArray[slide_num][1];
  document.getElementById('burns').innerHTML=imgArray[slide_num][2];
}

function slideshowUp() {
  num++;
  num = num % imgArray.length;
  slideshow(num);
}

function slideshowBack() {
  num--;
  if (num < 0) {num=imgArray.length-1;}
  num = num % imgArray.length;
  slideshow(num);
}