// Enjoy your stay. Code by evima

#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;// modint1000000007;// modint;

#include <bits/stdc++.h>

#define LOOPVAR_TYPE long long

#define all(x) (x).begin(), (x).end()
#define sz(x) ((LOOPVAR_TYPE)(x).size())
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define print(x) cout << (x) << endl
#define _rep(i, n) _rep2(i, 0, n)
#define _rep2(i, a, b) for(LOOPVAR_TYPE i = (LOOPVAR_TYPE)(a); i < (LOOPVAR_TYPE)(b); i++)
#define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)

template<class T> bool chmin(T &a, const T &b) { return (b < a) ? (a = b, true) : false; }
template<class T> bool chmax(T &a, const T &b) { return (a < b) ? (a = b, true) : false; }

#define eb emplace_back
#define fir first
#define sec second
#define mp make_pair
#define mt make_tuple

const long double EPS = 1e-9;
const long double PI = 3.14159265358979323846L;
const long long INF = 1070000000LL;
const long long MOD = 998244353LL;// 1000000007LL;

using namespace std;
using ld = long double;
using ll = long long;

void quit(const string& s) { print(s); exit(0); }

int N, M, S, T, p[100010];
vector<int> g[100010];

int main() {
    cin.tie(NULL);
    ios_base::sync_with_stdio(false);
    
    cin >> N >> M >> S >> T, --S;
    rep(i, N) cin >> p[i];
    rep(i, M){
        int a, b;
        cin >> a >> b, --a, --b;
        g[a].eb(b);
        g[b].eb(a);
    }

    vector<pair<int, int>> v;
    rep(i, N){
        v.eb(p[i], i);
    }
    sort(all(v));
    reverse(all(v));
    
    dsu d(N);
    int ans = 0, Y = p[S];
    for(auto [q, t]: v){
        if(q < Y){
            if(any_of(all(g[t]), [&](int u){ return d.same(u, S); })){
                ++ans;
                Y = q;
            }
        }
        for(int w: g[t]){
            d.merge(w, t);
        }
    }
    print(ans);
}