#include "highway.h"
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/trie_policy.hpp>
#define pb push_back
#define mp make_pair
#define taskname "A"
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> ii;
typedef tree <int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
const int maxn = 90000 + 5;
const int logn = log2(maxn) + 1;
int n , m;
vector<ii> adj[maxn];
int par[2][maxn];
int dis[2][maxn];
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
n = N;m = U.size();
// return;
ll initial = ask(vector<int>(m , 0));
int l = 0 , h = m - 1;
while(l < h){
int mid = l + h >> 1;
vector<int> val(m , 0);
for(int i = 0 ; i <= mid ; ++i)val[i] = 1;
if(ask(val) > initial)h = mid;
else l = mid + 1;
}
for(int i = 0 ; i < m ; ++i){
adj[U[i]].pb(mp(V[i] , i));
adj[V[i]].pb(mp(U[i] , i));
}
memset(par,-1,sizeof par);
memset(dis,123,sizeof dis);
auto bfs = [&](int dis[] , int par[] , int st){
dis[st] = 0;queue<int> q;q.push(st);
while(q.size()){
auto u = q.front();q.pop();
for(auto & c : adj[u]){
if(dis[c.first] > dis[u] + 1){
dis[c.first] = dis[u] + 1;q.push(c.first);
par[c.first] = c.second;
}
}
}
};
int u = U[l] , v = V[l];
vector<int> valU , valV;
bfs(dis[0] , par[0] , u);
bfs(dis[1] , par[1] , v);
for(int i = 0 ; i < n ; ++i){
if(dis[0][i] < dis[1][i])valU.pb(i);
else if(dis[0][i] > dis[1][i])valV.pb(i);
}
// cout << U[l] << " " << V[l] << endl;
auto solve = [&](int & res , vector<int> & val , int dis[] , int par[]){
sort(val.begin(),val.end(),[&](const int u , const int v){return dis[u] < dis[v];});
int l = 0 , h = (int)val.size() - 1;
while(l < h){
int mid = l + h >> 1;
vector<int> query(m , 0);
for(int i = mid ; i < val.size() ; ++i){
if(par[val[i]] != -1)query[par[val[i]]] = 1;
}
if(ask(query) > initial)l = mid + 1;
else h = mid;
}
// cout << val.size() << " " << val[l] << endl;
res = val[l];
};
solve(u , valU , dis[0] , par[0]);
solve(v , valV , dis[1] , par[1]);
answer(u,v);
}
#ifdef LOCAL
#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;
}
int main() {
freopen(taskname".INP","r",stdin);
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 // LOCAL
