#include <bits/stdc++.h>

using namespace std; const int maxn = 2e5 + 5; typedef long long ll;

int n, m, A, B;

vector<int> G[maxn];

int l[maxn];

int lev[maxn];

priority_queue<pair<int, int> > q; bool vs[maxn];

int at[maxn];

vector<int> tg[maxn];

inline void insert(int u, int t)
{
    if (vs[u]) return;
    vs[u] = 1;
    if (at[u] > n) return;
    tg[max(t + 1, at[u])].push_back(u);
}

queue<int> Q;

inline void solve()
{
    scanf("%d%d%d%d", &n, &m, &A, &B);
    for (int i = 1; i <= n; i++) G[i].clear(), vs[i] = 0;
    for (int i = 1, u, v; i <= m; i++) scanf("%d%d", &u, &v), G[u].push_back(v), G[v].push_back(u);
    for (int i = 1; i <= n; i++) scanf("%d", l + i);
    if (A <= B)
    {
        memset(lev, 63, sizeof(int) * (n + 1));
        lev[1] = 0;
        q.push({ 0, 1 });
        while (q.size())
        {
            int u = q.top().second; q.pop(); if (vs[u]) continue; vs[u] = 1;
            for (int v : G[u])
            {
                int nt = lev[u] + 1;
                if (nt < lev[v] && l[v] + (ll)B * nt <= l[1] + (ll)A * (nt - 1))
                {
                    q.push({ -(lev[v] = nt), v });
                }
            }
        }
        if (lev[n] < 1e9)
        {
            printf("%d\n", lev[n]);
        }
        else
        {
            puts("-1");
        }
    }
    else
    {
        for (int i = 2; i <= n; i++) at[i] = (l[i] + B <= l[1] ? 1 : 1 + (l[i] - l[1] + B + (A - B) - 1) / (A - B)); //, cerr << at[i] << ' '; cerr << endl;
        memset(lev, 63, sizeof(int) * (n + 1));
        lev[1] = 0;
        q.push({ 0, 1 });
        while (q.size())
        {
            int u = q.top().second; q.pop(); if (vs[u]) continue; vs[u] = 1;
            for (int v : G[u])
            {
                int nt = max(at[v], lev[u] + 1);
                if (nt < lev[v])
                {
                    q.push({ -(lev[v] = nt), v });
                }
            }
        }
        memset(vs, 0, sizeof(bool) * (n + 1));
        vs[1] = 1;
        int ti = lev[n];
        if (ti > n)
        {
            puts("-1");
            return;
        }
        for (int i = 0; i <= n; i++) tg[i].clear();
        for (int v : G[1]) insert(v, 0);
        for (int i = 1; i <= ti; i++)
        {
            for (int x : tg[i]) Q.push(x);
            if (!Q.size())
            {
                puts("-1");
                return;
            }
            int u = Q.front(); Q.pop();
            for (int v : G[u]) if (!vs[v]) insert(v, i);
        }
        while (Q.size()) Q.pop();
        printf("%d\n", ti);
    }
}

int main()
{
    int Tt; for (int i = 1; i <= Tt; i++) { if (i == 3678) { cin >> n >> m >> A >> B; printf("%d ", A-B); }
    return 0;
}

answer.code: In function ‘int main()’:
answer.code:110:2: error: expected ‘}’ at end of input
  110 | }
      |  ^
answer.code:107:1: note: to match this ‘{’
  107 | {
      | ^