#include "highway.h"
#include<bits/stdc++.h>
#define f first
#define s second
using namespace std;
const int Q = 2e5 + 5;
/*
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <utility>
#include <vector>
///#include "highway.h"
namespace {
const int MAX_NUM_CALLS = 100;
const long long INF = 1LL << 61;
int N, M, A, B, S, T;
std::vector<int> u, v;
std::vector<std::vector<std::pair<int, int> > > graph;
bool answered, wrong_pair;
int num_calls;
int read_int() {
int x;
if (scanf("%d", &x) != 1) {
fprintf(stderr, "Error while reading input\n");
exit(1);
}
return x;
}
void wrong_answer(const char *MSG) {
printf("Wrong Answer: %s\n", MSG);
exit(0);
}
} // namespace
long long ask(const std::vector<int> &w) {
if (++num_calls > MAX_NUM_CALLS) {
wrong_answer("more than 100 calls to ask");
}
if (w.size() != (size_t)M) {
wrong_answer("w is invalid");
}
for (size_t i = 0; i < w.size(); ++i) {
if (!(w[i] == 0 || w[i] == 1)) {
wrong_answer("w is invalid");
}
}
std::vector<bool> visited(N, false);
std::vector<long long> current_dist(N, INF);
std::queue<int> qa, qb;
qa.push(S);
current_dist[S] = 0;
while (!qa.empty() || !qb.empty()) {
int v;
if (qb.empty() ||
(!qa.empty() && current_dist[qa.front()] <= current_dist[qb.front()])) {
v = qa.front();
qa.pop();
} else {
v = qb.front();
qb.pop();
}
if (visited[v]) {
continue;
}
visited[v] = true;
long long d = current_dist[v];
if (v == T) {
return d;
}
for ( int t = 0; t < graph[v].size(); t++) {
pair<int,int> e = graph[v][t];
int vv = e.first;
int ei = e.second;
if (!visited[vv]) {
if (w[ei] == 0) {
if (current_dist[vv] > d + A) {
current_dist[vv] = d + A;
qa.push(vv);
}
} else {
if (current_dist[vv] > d + B) {
current_dist[vv] = d + B;
qb.push(vv);
}
}
}
}
}
return -1;
}
void answer(int s, int t) {
if (answered) {
wrong_answer("answered not exactly once");
}
if (!((s == S && t == T) || (s == T && t == S))) {
wrong_pair = true;
}
answered = true;
} */
/////////////////////////////////////////
int timer,out[Q],pos[Q],up[Q],c[Q];
vector<int> x;
vector<pair<int,int> > V[Q];
void dfs(int u,int p) {
for(int i=0;i<V[u].size();i++) {
if(V[u][i].f != p) up[V[u][i].f] = V[u][i].s,c[V[u][i].f] = u,dfs(V[u][i].f,u);
}
timer++;
pos[timer] = u;
}
void find_pair(int n, std::vector<int> u, std::vector<int> v, int A, int B) {
for(int i=0;i<u.size();i++){
V[u[i]].push_back({v[i],i});
V[v[i]].push_back({u[i],i});
}
dfs(0,-1);
x.resize(u.size());
int D = ask(x);
int l = 1, r = n - 1,S = -1, T = 0;
while(l<=r) {
int mid = (l+r)/2;
for(int i=1;i<n;i++) {
if(i < mid) x[up[pos[i]]] = 1;
else x[up[pos[i]]] = 0;
}
int d = ask(x);
if(d == D) {
S = pos[mid];
l = mid + 1;
}
else r = mid - 1;
}
for(int i = 0; i<n;i++) reverse(V[i].begin(),V[i].end());
timer = 0;
dfs(0,-1);
l = 1, r = n;
while(l<=r) {
int mid = (l+r)/2;
for(int i=1;i<n;i++) {
if(i < mid) x[up[pos[i]]] = 1;
else x[up[pos[i]]] = 0;
}
int d = ask(x);
if(d == D) {
T = pos[mid];
l = mid + 1;
}
else r = mid - 1;
}
for(int i=0;i<u.size();i++) x[i] = 1;
int e = S;
while(e) {
x[up[e]] = 0;
e = c[e];
}
if(ask(x) == D) {
D /= A;
T = S;
while(D--) {
T = c[T];
}
}
//cout<<S<<" "<<T<<endl;
answer(S,T);
}
/*
int main() {
N = read_int();
M = read_int();
A = read_int();
B = read_int();
S = read_int();
T = read_int();
u.resize(M);
v.resize(M);
graph.assign(N, std::vector<std::pair<int, int> >());
for (int i = 0; i < M; ++i) {
u[i] = read_int();
v[i] = read_int();
graph[u[i]].push_back({v[i], i});
graph[v[i]].push_back({u[i], i});
}
answered = false;
wrong_pair = false;
num_calls = 0;
find_pair(N, u, v, A, B);
if (!answered) {
wrong_answer("answered not exactly once");
}
if (wrong_pair) {
wrong_answer("{s, t} is wrong");
}
printf("Accepted: %d\n", num_calls);
return 0;
}*/
