window.onscroll = function() {
let scrolled = window.pageYOffset || document.documentElement.scrollTop;
let block = "page";
if (scrolled>99 & scrolled<200) {
block = "page1";
} else if (scrolled>=200 & scrolled<400) {
block = "page2";
} else if (scrolled>=400) {
block = "page3";
}
history.pushState({}, "", block);
}