var base = "mem_";
var loop = new Array('01', '02', '04', '06', '07', '08', '09', '10', '11', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22', '23', '24', '25', '26', '28', '29', '30', '31', '32', '33', '34');
var p_out_img = "page_parts/button_prev-dis.gif";
var n_out_img = "page_parts/button_next-dis.gif";

var prev_l = next_l = ''; 
var suffix = '';

function prev_alert() {
  alert('最初の選手です');
}

function next_alert() {
  alert('選手の末尾です');
}

function check_loop() {
  var url = location.href;
  var fname = url.split('/').pop().split('.');
  suffix = fname[1];
  var fnum = fname[0].split(base).pop();
  var ll = loop; var flag = 0;
  while(ll.length != 0 && flag < 2) {
    var num = ll.shift();
    if (num == fnum) {
      flag = 1;
    }
    else {
      if (flag == 0) {
	prev_l =  num;
      }
      else {
	next_l = num;
	flag = 2;
      }
    }
  }
  if (prev_l == '') {
    document.getElementById('prev').src = p_out_img;
  }
  if (next_l == '') {
    document.getElementById('next').src = n_out_img;
  }
}

function loop_prev() {
  if (prev_l != '') {
    location.href = base+prev_l+'.'+suffix;
  }
  else {
    prev_alert();
  }
}

function loop_next() {
  if (next_l != '') {
    location.href = base+next_l+'.'+suffix;
  }
  else {
    next_alert();
  }
}