use std::collections::*;
use std::ops::Bound::*;

fn main() {
    let n = read::<usize>();
    let mut a = BTreeSet::new();
    for i in 0..n {
        a.insert((read::<i64>(), i));
    }
    let mut ans = 0;
    while let Some(&(size, idx)) = a.iter().next() {
        ans += 1;
        let mut used = vec![(size, idx)];
        let mut cur = size;
        while let Some(&(ns, nidx)) = a.range((Included((cur + 2, 0)), Unbounded)).next() {
            used.push((ns, nidx));
            cur = ns;
        }
        for elem in used {
            a.remove(&elem);
        }
    }
    println!("{}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}