#include <bits/stdc++.h>
#include "highway.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
#define pb push_back
#define popb pop_back
#define all(x) (x).begin(),(x).end()
#define ff first
#define ss second
const int nax = 9e4 + 4;
vpi adj[nax];
int n, m, a, b;
int d[nax];
vi cor[nax];
int top[nax], sp[nax][20], tin[nax], tout[nax];
int max_d = 1;
int cureul = -1;
/*
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B);
long long ask(const std::vector<int> &w);
void answer(int s, int t);
*/
void dfs(int x, int p = 0)
{
sp[x][0] = p;
d[x] = d[p] + 1;
tin[x] = ++cureul;
max_d = max(max_d, d[x]);
cor[d[x]].pb(x);
for(auto e: adj[x])
{
if(e.ff != p)
{
top[e.ff] = e.ss;
dfs(e.ff,x);
}
}
tout[x] = ++cureul;
}
bool check_sub(int a, int b)
{
if(tin[a] >= tin[b] && tin[a] <= tout[b])
return true;
else
return false;
}
void find_pair(int N, vi U, vi V, int A, int B)
{
n = N;
m = U.size();
for(int i = 0 ; i < m; i++)
{
adj[U[i]].pb({V[i], i });
adj[V[i]].pb({U[i], i });
}
dfs(0);
int debut = 2;
int fin = max_d;
vi w(m, 0);
ll norm = ask(w);
int d_t = 2;
while(debut <= fin )
{
int mid = (debut + fin)/2;
w.assign(m, 0);
for(int i = mid; i <= max_d; i ++)
{
for(auto e: cor[i])
w[top[e]] = 1;
}
ll cb =ask(w);
if(cb > norm)
{
d_t = mid;
debut = mid +1 ;
}
else
fin = mid - 1;
}
debut = 0;
fin = (int)(cor[d_t].size()) - 1;
int t_idx = 0;
while(debut <= fin)
{
int mid = (debut + fin)/2;
w.assign(m, 0);
for(int i = 0; i <= mid; i ++)
w[top[cor[d_t][i]]] = 1;
ll cb = ask(w);
if(cb > norm)
{
t_idx = mid;
fin = mid - 1;
}
else
debut = mid + 1;
}
w.assign(m, 0);
int t = cor[d_t][t_idx];
int cur = t;
while(cur != 0)
{
w[top[cur]] = 1;
cur= sp[cur][0];
}
ll a= A;
ll b= B;
ll delt = 1ll * (ask(w) - norm);
delt /= (ll)(b - a);
int lca =t;
int avlast = t;
for(int i = 0; i < delt; i ++)
{
avlast= lca;
lca= sp[lca][0];
}
for(int i= 1; i <= max_d; i++)
{
cor[i].clear();
}
for(int i = 0 ; i < n; i++)
{
if(check_sub(i, lca))
{
if(!check_sub(i, avlast))
{
cor[d[i]].pb(i);
}
}
}
int d_s = d[lca];
debut = d[lca] + 1;
fin = max_d;
while(debut <= fin)
{
int mid= (debut + fin)/2;
w.assign(m, 0);
for(int i = mid; i<= fin; i ++)
for(auto e: cor[i])
w[top[e]] = 1;
ll cb = ask(w);
if(cb > norm)
{
d_s = mid;
debut = mid + 1;
}
else
fin = mid - 1;
}
if(d_s == d[lca])
{
answer(lca, t);
return ;
}
int s_idx = 0;
debut = 0 ;
fin = (int)(cor[d_s].size()) - 1;
while(debut <= fin)
{
int mid= (debut + fin)/2;
w.assign(m, 0);
for(int i = debut ; i <= mid; i ++)
w[top[cor[d_s][i]]] = 1;
ll cb = ask(w);
if(cb > norm)
{
s_idx = mid;
fin = mid - 1;
}
else
debut = mid + 1;
}
int s= cor[d_s][s_idx];
answer(s,t);
}
/*
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;
}
/*
12 11 5 9 1 11
0 1
1 2
1 3
2 7
3 9
3 8
0 6
0 4
0 5
4 11
6 10
*/
