#include <bits/stdc++.h>
#define fast ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL)
#define ll long long int
#define ld long double
using namespace std;
const int N = 1e6 + 5;
const int MOD = 1e9 + 7;
vector<int> graph[N];
bool vis[N];
int mx = 0, node;
 
void dfs(int source, int far){
	vis[source] = 1;
	if(far > mx){
		mx = far;
		node = source;
	}
	for(auto k : graph[source])
		if(!vis[k])
			dfs(k, far + 1);
}	
 
int main(){
	fast;
	int n;
	cin >> n;
	for(int i = 0; i < n - 1; ++i){
		int u, v;
		cin >> u >> v;
		graph[u].push_back(v);
		graph[v].push_back(u);
	}
	dfs(1, 0);
	memset(vis, 0, sizeof(vis));
	dfs(node, 0);
	cout << 3 * mx << '\n';
	return 0;
}

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