use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let v: Vec<i32> = s.split_whitespace().flat_map(str::parse).collect();
	let mut p = true;
	let a = v
		.chunks(2)
		.filter(|&v| {
			let q = p;
			p = (v[0] - 1) % (v[1] + 1) != 0;
			p ^ q
		})
		.count();
	println!("{}", a)
}