var c = 0
var s
function photoGallery() {
    if (c % 5 == 0) {

        document.getElementById('photo-gallery').src = "photos/pic1.jpg";
    }
    if (c % 5 == 1) {

        document.getElementById('photo-gallery').src = "photos/pic2.jpg";
    }
    if (c % 5 == 2) {

        document.getElementById('photo-gallery').src = "photos/pic3.jpg";
    }
    if (c % 5 == 3) {
        document.getElementById('photo-gallery').src = "photos/pic4.jpg";
    }
    if (c % 5 == 4) {
        document.getElementById('photo-gallery').src = "photos/pic5.jpg";
    }
    c = c + 1
    s = setTimeout("photoGallery()", 5000)
}