#include <bits/stdc++.h>
#define int long long
#define pb push_back
using namespace std;

const int N = 3e5 + 10;
vector<int> gr[N];


//dist vert
pair<int,int> diam(int v, int pr = -1, int d = 0) {
	int bg = v;
	for(auto it: gr[v]) {
		if(it == pr) continue;
		pair<int,int> tmp = diam(it, v);
		if(tmp.first > d) {
    	bg = tmp.second;
    	d = tmp.first;
    }
	}
	return {d + 1, bg};
}
main() {
	int n;
	cin >> n;
	for(int i = 1; i < n; i++) {
		int l, r;
		cin >> l >> r;
		gr[l].pb(r);
		gr[r].pb(l);
	}
	int l = diam(1).second;
	int d = diam(l).first - 1;
	cout << d * 3 << endl;
}