function toggle(num) {
  var container = document.getElementById('content');
  var children = container.getElementsByTagName('div');
  for (var i = 0; i < children.length; i++) {
    id = children[i].id.split('_')[1];
    if (id == num + 1) {
      children[i].className = 'people visible';
    } else {
      children[i].className = 'people hidden';
    }
  }
}