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#include <bits/stdc++.h>
#include <vector>
#define all(vec) vec.begin(), vec.end()
#define PB push_back
#define PF push_front
#define EB emplace_back
#define EF emplace_front
#define EM emplace
#define FI first
#define SE second
#define pct __builtin_popcountll
#define ctz __builtin_ctzll
#define lson(o) (o << 1)
#define rson(o) (o << 1 | 1)
#define SZ(a) ((long long)a.size())
#define FOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define ROF(i, a, b) for (int i = (a); i >= (b); --i)
#define debug(var) cerr << #var << ":" << var << "\n";
#define cend cerr << "\n-----------\n"
#define fsp(x) fixed << setprecision(x)
#define minn(vec) *min_element(vec.begin(), vec.end())
#define maxx(vec) *max_element(vec.begin(), vec.end())
#define yyy cout << "YES\n"
#define nnn cout << "NO\n"
using namespace std;
using ll = long long;
using ull = unsigned long long;
using DB = double;
using LD = long double;
using i128 = __int128;
using CD = complex<double>;
static constexpr ll MAXN = (ll)1e6 + 10, INF = (1ll << 61) - 1;
static constexpr ll mod = (ll)1e9 + 7;
static constexpr double eps = 1e-8;
const double pi = acos(-1.0);
ll N, M, Q, X, K, T, lT, S, E;
void Solve() {
cin >> N >> M >> S >> E;
vector<ll> A(N + 4);
FOR(i, 1, N) { cin >> A[i]; }
vector<vector<ll>> g(N + 5);
FOR(i, 1, M) {
ll u, v;
cin >> u >> v;
g[u].PB(v);
}
vector<ll> tin(N + 5), low(N + 5);
vector<ll> stk;
vector<char> instk(N + 5);
vector<ll> scc(N + 5);
vector<ll> scca(N+5);
ll idx = 0, sccidx = 0;
auto dfs1 = [&](auto self, ll u) -> void {
tin[u] = low[u] = ++idx;
stk.PB(u);
instk[u] = 1;
for (auto v : g[u]) {
if (!tin[v]) {
self(self, v);
low[u] = min(low[u], low[v]);
} else if (instk[v]) {
low[u] = min(low[u], low[v]);
}
}
if (tin[u] == low[u]) {
++sccidx;
ll y=0;
do {
y = stk.back();
stk.pop_back();
instk[y] = 0;
scc[y] = sccidx;
scca[sccidx]+=A[y];
} while (y != u);
}
};
FOR(i,1,N){
if(!tin[i]){
dfs1(dfs1,i);
}
}
vector<vector<ll> > scg(sccidx+5);
vector<ll> dp(sccidx+5,-INF);
vector<ll> in(sccidx+5);
FOR(u,1,N){
for(auto v:g[u]){
if(scc[u]==scc[v]) continue;
scg[scc[u]].PB(scc[v]);
in[scc[v]]++;
}
}
queue<ll> q;
FOR(i,1,sccidx){
if(in[i]==0){
q.push(i);
}
}
dp[scc[S]]=scca[scc[S]];
while(!q.empty()){
auto u=q.front();q.pop();
for(auto v:scg[u]){
dp[v]=max(dp[v],dp[u]+scca[v]);
in[v]--;
if(in[v]==0){
q.push(v);
}
}
}
ll ans=0;
cout<<(ll)dp[scc[E]]<<"\n";
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
Solve();
return 0;
}
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