#include "highway.h"
#include<bits/stdc++.h>
using namespace std;
/*
namespace {
constexpr int MAX_NUM_CALLS = 100;
constexpr 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 (auto e : graph[v]) {
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;
}
*/
const int nmax=1e5+42;
vector< pair<int,int> > adj[nmax];
int n,m,a,b;
vector<int> idle;
long long mem_d;
int dist[nmax];
queue<int> q;
vector<int> mem_U,mem_V;
int solve(int from,int blocked)
{
memset(dist,-1,sizeof(dist));
dist[from]=0;
vector<int> valid_edges={};
q.push(from);
while(q.size())
{
int node=q.front();
q.pop();
for(auto w:adj[node])
if(w.second!=blocked&&dist[w.first]==-1)
{
dist[w.first]=dist[node]+1;
valid_edges.push_back(w.second);
q.push(w.first);
}
}
if(valid_edges.size()==0)return from;
int ok=valid_edges.size()-1,not_ok=-2;
while(ok-not_ok>1)
{
int av=(ok+not_ok)/2;
vector<int> cur=idle;
for(int j=av+1;j<valid_edges.size();j++)
cur[valid_edges[j]]=1;
if(ask(cur)==mem_d)ok=av;
else not_ok=av;
}
//cout<<"valid= ";for(auto w:valid_edges)cout<<w<<" ";cout<<endl;
//cout<<"ok= "<<ok<<endl;
if(ok==-1)return from;
int u=mem_U[valid_edges[ok]];
int v=mem_V[valid_edges[ok]];
//cout<<"u= "<<u<<" v= "<<v<<endl;
if(dist[u]<dist[v])return v;
return u;
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B)
{
n=N;
m=U.size();
a=A;
b=B;
for(int i=0;i<m;i++)idle.push_back(0);
for(int i=0;i<m;i++)
{
adj[U[i]].push_back({V[i],i});
adj[V[i]].push_back({U[i],i});
}
mem_U=U;
mem_V=V;
mem_d=ask(idle);
int ok=m-1,not_ok=-1;
while(ok-not_ok>1)
{
int av=(ok+not_ok)/2;
vector<int> me=idle;
for(int j=0;j<=av;j++)me[j]=1;
if(ask(me)>mem_d)ok=av;
else not_ok=av;
}
//cout<<"edge "<<U[ok]<<" "<<V[ok]<<endl;
int s=solve(U[ok],ok);
int t=solve(V[ok],ok);
//cout<<"s= "<<s<<" t= "<<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;
}
*/
