function share_facebook(url) {
	window.open('http://www.facebook.com/sharer/sharer.php?u=' + url);
}
function share_twitter(url) {
	window.open('https://twitter.com/share?url=' + url);
}
function share_gplus(url) {
	window.open('https://plus.google.com/share?url=' + url);
}
function share_vk(url) {
	window.open('http://vk.com/share.php?url=' + url);
}