#include <bits/stdc++.h>
using namespace std;
 
#define show(x) cout << (#x) << " is " << (x) << endl
#define ll long long
#define len(s) (int)s.length()
#define epb emplace_back
#define fir first
#define sed second
#define sz(ds) (int)ds.size()
#define all(arr) arr.begin(), arr.end()
 
 
const int maxn = 1e6 + 5;
int n, m, s, e;
vector<int> adj[maxn], rv_adj[maxn];
int pass[maxn];
ll val[maxn];
 
vector<int> st;
 
vector<int> dag[maxn];
vector< vector<int> > comps;
int comp_of[maxn];
ll sum_of[maxn];
ll dp[maxn];
 
bool contain_e[maxn];

vector<int> ord;
 
void dfs_1(int u){
	pass[u] = true;
	for(auto v : adj[u]){
		if(!pass[v]) dfs_1(v);
	}
	ord.epb(u);
}
 
void dfs_2(int u){
	pass[u] = true;
	st.epb(u);
	for(auto v : rv_adj[u]){
		if (!pass[v]) dfs_2(v);
	}
}

 
int main() {
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	//
	cin >> n >> m >> s >> e;
	for (int i = 1 ; i <= n ; i++) cin >> val[i];
	for (int i = 0 ; i <  m ; i++) {
		int u, v;
		cin >> u >> v;
		adj[u].epb(v);
		rv_adj[v].epb(u);
	}
 
 
	for(int i = 1 ; i <= n ;i++){
		if(!pass[i])
			dfs_1(i);
	}

	// dfs_1(s)

	reverse(ord.begin(),ord.end());
 
	fill(pass,pass+maxn,false);
 
	for(auto i : ord){
		if(!pass[i]){
			dfs_2(i);
 
			ll tmp = 0;
			ll nx_idx = sz(comps);
			for (auto v : st) {
				if (v == e) contain_e[nx_idx] = true;
				tmp += val[v];
				comp_of[v] = nx_idx;
			}
 
			sum_of[nx_idx] = tmp;
 
			comps.epb(st);
 
			st.clear();
 
		}
	}

 
	for (int i = 1 ; i <= n ; i++) {
		for (auto v : adj[i]) {
			int comp_i = comp_of[i];
			int comp_v = comp_of[v];
			if (comp_i != comp_v) {
				dag[comp_i].epb(comp_v);
			}
		}
	}
 
	fill(pass,pass+maxn,false);
 
	function<void(int,int)> dfs = [&](int u, int p){
 
		pass[u] = true;
	
		ll max_e = 0;
 
		for(auto v : dag[u]){
			assert(v != p);
			if (!pass[v]){
				dfs(v,u);
			}
			if (contain_e[v]){
				max_e = max(max_e,dp[v]);
			}
		}
 
		if(contain_e[u] || max_e > 0){
			dp[u] += (max_e + sum_of[u]);
			contain_e[u] = true;
		}
 
 
	};
 
	dfs(comp_of[s], -1);
 
	cout << dp[comp_of[s]];
 
}