Scanf.scanf "%d %d" (fun n m ->
    let rec loop i pos time =
        if i = m then true else
            let t, p = Scanf.scanf " %d %d" (fun t p -> t, p) in
            if abs (pos - p) <= t - time then loop (i + 1) p t else false
    in
    print_endline @@ if loop 0 0 0 then "Yes" else "No"
)