#include <iostream>
#include <vector>
#include "highway.h"
#include <cassert>
#define int long long
using namespace std;
vector<vector<pair<int, int>>> cons;
vector<signed> w;
void dfs(int i, int from, int d, vector<vector<pair<int, int>>>& put){
for(pair<int, int> p : cons[i]){
int c = p.first, m = p.second;
if(c == from) continue;
put[d+1].push_back({c, m});
w[m] = 1;
dfs(c, i, d+1, put);
}
}
void find_pair(signed N, vector<signed> U, vector<signed> V, signed A, signed B) {
int M = U.size();
cons = vector<vector<pair<int, int>>> (N);
for(int m = 0; m < M; m++){
cons[U[m]].push_back({V[m], m});
cons[V[m]].push_back({U[m], m});
}
int dst = ask(vector<signed> (M))/A;
auto qrange = [&](int ll, int rl){
vector<signed> wl(M);
for(int i = ll; i < rl; i++) wl[i] = 1;
return ask(wl) != dst*A;
};
int l = 0, r = M;
while(l + 1 < r){
int m = l + (r-l)/2;
if(qrange(l, m)) r = m;
else l = m;
}
vector<vector<pair<int, int>>> side1 (N);
vector<vector<pair<int, int>>> side2 (N);
w = vector<signed>(M);
dfs(U[l], V[l], 0, side1);
w = vector<signed>(M);
dfs(V[l], U[l], 0, side2);
int dst2 = (ask(w)-dst*A)/(B-A);
auto bs_sel = [&](vector<pair<int, int>> sel){
int l = 0, r = sel.size();
while(l + 1 < r){
int m = l + (r-l)/2;
vector<signed> lw (M);
for(int set = l; set < m; set++) lw[sel[set].second] = 1;
if(ask(lw) != dst*A) r = m;
else l = m;
}
return sel[l].first;
};
int u, s;
if(dst2 > 0) u = bs_sel(side2[dst2]);
else u = V[l];
if(dst-dst2-1 > 0) s = bs_sel(side1[dst-dst2-1]);
else s = U[l];
answer(u, s);
}
/*
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <utility>
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;
}
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;
}
*/
