#line 2 "/Users/tiramister/CompetitiveProgramming/Cpp/CppLibrary/Tools/heap_alias.hpp"

#include <queue>

template <class T>
using MaxHeap = std::priority_queue<T>;
template <class T>
using MinHeap = std::priority_queue<T, std::vector<T>, std::greater<T>>;
#line 2 "/Users/tiramister/CompetitiveProgramming/Cpp/CppLibrary/Graph/graph.hpp"

#include <vector>

template <class Cost = int>
struct Edge {
    int src, dst;
    Cost cost;

    Edge() = default;
    Edge(int src, int dst, Cost cost = 1)
        : src(src), dst(dst), cost(cost){};

    bool operator<(const Edge<Cost>& e) const { return cost < e.cost; }
    bool operator>(const Edge<Cost>& e) const { return cost > e.cost; }
};

template <class Cost = int>
struct Graph : public std::vector<std::vector<Edge<Cost>>> {
    using std::vector<std::vector<Edge<Cost>>>::vector;

    void span(bool direct, int src, int dst, Cost cost = 1) {
        (*this)[src].emplace_back(src, dst, cost);
        if (!direct) (*this)[dst].emplace_back(dst, src, cost);
    }
};
#line 3 "main.cpp"
#include <iostream>
#include <algorithm>
#line 6 "main.cpp"

using namespace std;

void solve() {
    int n, m, s, t;
    cin >> n >> m >> s >> t;
    --s;

    vector<int> xs(n);
    for (auto& x : xs) cin >> x;

    Graph<> graph(n);
    while (m--) {
        int u, v;
        cin >> u >> v;
        graph.span(false, --u, --v);
    }

    vector<bool> vis(n, false);
    MaxHeap<pair<int, int>> heap;

    vis[s] = true;
    heap.emplace(xs[s], s);

    int xmin = xs[s], y = 0;
    while (!heap.empty()) {
        auto [x, v] = heap.top();
        heap.pop();
        if (x < xmin) {
            ++y;
            xmin = x;
        }

        for (auto e : graph[v]) {
            int u = e.dst;
            if (vis[u]) continue;

            vis[u] = true;
            heap.emplace(xs[u], u);
        }
    }

    cout << y << "\n";
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}