// ---------- begin chmin, chmax ----------
pub trait ChangeMinMax {
    fn chmin(&mut self, x: Self) -> bool;
    fn chmax(&mut self, x: Self) -> bool;
}

impl<T: PartialOrd> ChangeMinMax for T {
    fn chmin(&mut self, x: Self) -> bool {
        *self > x && {
            *self = x;
            true
        }
    }
    fn chmax(&mut self, x: Self) -> bool {
        *self < x && {
            *self = x;
            true
        }
    }
}
// ---------- end chmin, chmax ----------
// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------

fn run() {
    input! {
        n: usize,
        e: [(usize1, usize1); n - 1],
    }
    let mut g = vec![vec![]; n];
    for (a, b) in e {
        g[a].push(b);
        g[b].push(a);
    }
    let mut topo = vec![0];
    for i in 0..n {
        let v = topo[i];
        topo.extend(&g[v]);
        for u in g[v].clone() {
            g[u].retain(|p| *p != v);
        }
    }
    let mut dp = vec![std::collections::BinaryHeap::new(); n];
    let mut half = vec![1; n];
    let mut ans = 1;
    for &v in topo.iter().rev() {
        let mut a = vec![];
        for &u in g[v].iter() {
            a.push((half[u], u));
        }
        a.sort();
        let mut next_half = 1;
        for &u in g[v].iter() {
            let mut len = 0;
            len += *dp[u].peek().unwrap();
            len += 1;
            len += a.iter().rev().find(|p| p.1 != u).map_or(0, |p| p.0);
            next_half.chmax(len);
            let mut len = 0;
            len += *dp[u].peek().unwrap();
            len += 1;
            if dp[u].len() > 1 {
                let x = dp[u].pop().unwrap();
                let y = dp[u].pop().unwrap();
                len += y;
                dp[u].push(x);
                dp[u].push(y);
            }
            next_half.chmax(len);
        }
        let mut h = std::collections::BinaryHeap::new();
        for &u in g[v].iter() {
            h.append(&mut dp[u]);
        }
        if h.len() > 1 {
            let a = h.pop().unwrap();
            let b = h.pop().unwrap();
            h.push(a + b + 1);
        } else {
            h.push(1);
        }
        next_half.chmax(*h.peek().unwrap());
        dp[v] = h;
        half[v] = next_half;
    }
    ans.chmax(half[0]);
    ans.chmax(*dp[0].peek().unwrap());
    println!("{}", ans);
}

fn main() {
    run();
}