#include "diameter.h"
#include<bits/stdc++.h>
#define fst first
#define scd second
#define SZ(s) ((int)s.size())
#define all(s) s.begin(),s.end()
#define eb emplace_back
const int N=1e6+5;
using namespace std;
typedef pair<int,int> pii;
template<class T,class I> inline bool chkmax(T &a,I b){return b>a?a=b,1:0;}
template<class T,class I> inline bool chkmin(T &a,I b){return b<a?a=b,1:0;}

// grader.cpp -------------------------------------
/*
namespace {
static void WA(std::string err) {
	std::cout << "WA: " << err << std::endl;
	exit(0);
}

static int subid, n;
static std::vector<int> e[N];

static int fa[N], dep[N], cnt, p[N], pos[N], l[N], r[N];
static void dfs(int u) {
	p[++cnt] = u, pos[u] = cnt;
	dep[u] = dep[fa[u]] + 1;
	l[u] = cnt;
	for (auto v : e[u])
		if (v != fa[u]) {
			fa[v] = u, dfs(v);
			p[++cnt] = u;
		}
	r[u] = cnt;
}

static int lg[N];
static std::pair<int, int> mn[N][20];
static void init() {
	cnt = 0, dfs(1), lg[0] = -1;
	for (int i = 1; i <= cnt; i++) {
		mn[i][0] = std::make_pair(dep[p[i]], p[i]);
		lg[i] = lg[i >> 1] + 1;
	}
	for (int j = 1; j <= lg[cnt]; j++) {
		for (int i = 1; i <= cnt - (1 << j) + 1; i++) {
			mn[i][j] = std::min(mn[i][j - 1], mn[i + (1 << (j - 1))][j - 1]);
		}
	}
}
static int LCA(int x, int y) {
	int l = pos[x], r = pos[y];
	if (l > r) std::swap(l, r);
	int tmp = lg[r - l + 1];
	return std::min(mn[l][tmp], mn[r - (1 << tmp) + 1][tmp]).second;
}

static int cntq2;
static int cntq1;

static int dis(int x, int y) { return dep[x] + dep[y] - 2 * dep[LCA(x, y)]; }

static void solve() {
	cntq1 = cntq2 = 0;
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) e[i].clear();
	for (int i = 1; i < n; i++) {
		int x, y;
		scanf("%d%d", &x, &y);
		e[x].push_back(y);
		e[y].push_back(x);
	}
	init();
	std::pair<int, int> ans = find_diameter(subid, n);
	int x = 1, y = 1;
	for (int i = 1; i <= n; i++)
		if (dis(x, i) > dis(x, y)) y = i;
	x = y, y = 1;
	for (int i = 1; i <= n; i++)
		if (dis(x, i) > dis(x, y)) y = i;
	if (ans.first < 1 || ans.first > n) {
		WA("find wrong diameter!");
	}
	if (ans.second < 1 || ans.second > n) {
		WA("find wrong diameter!");
	}
	if (dis(x, y) != dis(ans.first, ans.second)) {
		WA("find wrong diameter!");
	}
}
}  // namespace
bool in(int x, int y, int z) {
	if (x < 1 || x > n) WA("ask2 format error");
	if (y < 1 || y > n) WA("ask2 format error");
	if (z < 1 || z > n) WA("ask2 format error");
	++cntq2;
	if (cntq2 > 2) {
		WA("too many ask2");
	}
	int cnt = 0;
	if (pos[y] >= l[x] && pos[y] <= r[x]) ++cnt;
	if (pos[z] >= l[x] && pos[z] <= r[x]) ++cnt;
	if (cnt == 1) return 1;
	return LCA(y, z) == x;
}

int query(int x, int y, int z) {
	printf("ask %d %d %d\n",x,y,z);
	if (x == y || y == z || x == z) WA("ask1 format error");
	if (x < 1 || x > n) WA("ask1 format error");
	if (y < 1 || y > n) WA("ask1 format error");
	if (z < 1 || z > n) WA("ask1 format error");
	++cntq1;
	if (cntq1 > 300000) {
		WA("too many ask1");
	}
	return dis(x, y) + dis(x, z) + dis(y, z);
}
// end --------------------------------------------------------------------------
*/
bool vis[N];
std::pair<int, int> find_diameter(int task_id, int n){
	if(n<=2) return pii(1,n);
	for(int i=1;i<=n;++i) vis[i]=0;
	vector<int> dis(n+1);
	int mn=1e9;
	for(int i=2;i<n;++i){
		dis[i]=query(1,i,n);
		chkmin(mn,dis[i]);
	}
	vector<int> chain;
	chain.eb(1);
	for(int i=2;i<n;++i){
		if(dis[i]==mn) chain.eb(i);
	}
	chain.eb(n);
	if(SZ(chain)==n) return pii(1,n); 
	int u=0,v=0;
	for(int i=2;i<n;++i){
		if(dis[i]==mn+2){
			u=i;
			break;
		}
	}
	mn=1e9;
	vector<int> rdis(n+1);
	for(int v:chain){
		if(v==1) continue; 
		rdis[v]=query(1,v,u);
		chkmin(mn,rdis[v]);
	}
	for(int x:chain){
		if(rdis[x]==mn){
			if(!in(x,1,u)){
				v=1;
				break;
			}
		}
	}
	if(!v){
		rdis[1]=mn;
		vector<int> black;
		for(int v:chain){
			if(rdis[v]==mn) black.eb(v);
		}
		pii res(0,black[1]);
		for(int i=2;i<SZ(black);++i){
			int v=black[i],len=query(1,res.scd,v);
			if(i==2){
				res.fst=len;
				if(in(res.scd,1,v)) res.scd=v;
			}else{
				if(len!=res.scd) res=pii(v,len);
			}
		}
		v=res.scd;	
	}
	for(int v:chain) vis[v]=1;
	vis[1]=vis[n]=0;
	vis[u]=vis[v]=1;
	vector<int> D(n+1);
	pii Lpoint(0,0);
	for(int i=1;i<=n;++i){
		if(!vis[i]){
			D[i]=query(u,v,i);
			if(D[i]==dis[i]-mn) D[i]=(D[i]-2)/2;
			else D[i]/=2;
			chkmax(Lpoint,pii(D[i],i));
		}
	}
	D[v]=1,vis[v]=0;
	pii Rpoint(0,0);
	vis[Lpoint.scd]=1;
	for(int i=1;i<=n;++i){
		if(!vis[i]){
			int x=query(u,Lpoint.scd,i)-D[Lpoint.scd]-D[i];
			chkmax(Rpoint,pii(x,i));
		}
	}
	chkmax(Rpoint,pii(D[Lpoint.scd],u));
	return pii(Lpoint.scd,Rpoint.scd);
}
//signed main(){
//	int T;
//	scanf("%d%d", &subid, &T);
//	while (T--) solve();
//	printf("correct\n");
//	return 0;
//}