#include <bits/stdc++.h>
using namespace std;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

int main() {
    int n, m, s, t; cin >> n >> m >> s >> t; --s; --t;
    auto p = vec<int>(uns, n);
    for (auto &e : p) cin >> e;

    auto g = vec<int>(uns, n, 0);
    for (int i = 0; i < m; ++i) {
        int a, b; cin >> a >> b; --a; --b;
        g[a].push_back(b);
        g[b].push_back(a);
    }

    int x = p[s], y = 0;

    auto vis = vec<bool>(false, n);
    priority_queue<tuple<int, int>> que;
    que.push({ p[s], s });
    while (!que.empty()) {
        auto [c, u] = que.top(); que.pop();
        if (vis[u]) continue;
        vis[u] = true;

        y += c < x;
        x = min(x, c);

        for (auto v : g[u]) {
            if (vis[v]) continue;
            que.push({ p[v], v });
        }
    }

    cout << y << endl;
}