fn main() {
    let ccount = 1000;
    let csize = 10;
    let n = csize * ccount + 1;
    let mut ans = Vec::new();
    for offset in (0..ccount).map(|cid| cid * csize) {
        ans.extend(
            [
                (0, 1),
                (0, 2),
                (0, 3),
                (1, 4),
                (1, 5),
                (2, 6),
                (2, 7),
                (3, 8),
                (3, 9),
            ]
            .iter()
            .map(|(i, j)| (i + offset, j + offset)),
        );
        ans.push((n - 1, offset));
    }
    println!("{n}");
    for (i, j) in ans {
        let i = i + 1;
        let j = j + 1;
        println!("{i} {j}");
    }
}