#ifndef EVAL
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <utility>
#include <vector>
//#include "highway.h"
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;
}
#endif // EVAL
#include <bits/stdc++.h>
#include "highway.h"
using namespace std;
#define all(x) x.begin(), x.end()
#define pb push_back
#define ln '\n'
//#define int long long
template <class _T>
bool chmin(_T &x, const _T &y){
bool flag = false;
if ( x > y ){
x = y; flag |= true;
}
return flag;
}
template <class _T>
bool chmax(_T &x, const _T &y){
bool flag = false;
if ( x < y ){
x = y; flag |= true;
}
return flag;
}
void find_pair(int n, vector<int> U, vector<int> V, int A, int B) {
int m = (int)U.size();
assert(m == n - 1);
vector <pair<int,int>> g[n], edge(m);
vector <int> tree;
for ( int i = 0; i < m; i++ ){
g[U[i]].pb({V[i], i});
g[V[i]].pb({U[i], i});
}
function <void(int,int)> dfs = [&](int x, int par){
for ( auto [to, id]: g[x] ){
if ( to == par ){
continue;
} tree.pb(id);
edge[id] = {x, to};
dfs(to, x);
}
};
dfs(0, -1);
int dis = ask(vector <int> (m, 0)) / A * B;
auto get = [&](int root){
tree.clear();
dfs(root, -1);
int l = 0, r = m - 1;
while ( l < r ){
int md = (l + r) >> 1;
vector <int> f(m, 0);
for ( int i = 0; i <= md; i++ ){
f[tree[i]] = 1;
}
if ( ask(f) == dis ) r = md;
else l = md + 1;
}
return edge[tree[l]].second;
};
int root = -1;
for ( int i = 0; i < n; i++ ){
if ( (int)g[i].size() == 1 ){
root = i;
}
}
int s = get(root), t = get(s);
answer(s, t);
}
#ifndef EVAL
/*
4 4 1 3
1 3
0 1
0 2
0 3
1 2
7 6 1 2
5 3
0 1
0 2
1 3
1 4
2 5
4 6
*/
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;
}
#endif // EVAL
