#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <list>
#include <iterator>
#include <cassert>
#include <numeric>
#include <functional>
#include <ctime>
#pragma warning(disable:4996) 

//#define ATCODER
#ifdef ATCODER
#include <atcoder/all>
#endif

typedef long long ll;
typedef unsigned long long ull;
#define LINF  9223300000000000000
#define LINF2 1223300000000000000
#define LINF3 1000000000000
#define INF 2140000000
const long long MOD = 1000000007;
//const long long MOD = 998244353;

using namespace std;
#ifdef ATCODER
using namespace atcoder;
#endif

class UF
{
private:
    int         num;
    vector<int> par;
    vector<int> siz;
public:
    //vector<int> val;
public:
    UF(int n) : num(n) {
        par.resize(n);
        siz.resize(n);
        //val.resize(n);
        int i;
        for (i = 0; i < n; i++) {
            par[i] = i; siz[i] = 1;
            //val[i]=0;
        }
    }

    int find(int x) {
        if (x == par[x]) return x;
        return par[x] = find(par[x]);
    }

    void unite(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) return;
        if (siz[x] < siz[y]) {
            par[x] = y;
            siz[y] = siz[x] + siz[y];
            //val[y]=val[x]+val[y];
        }
        else {
            par[y] = x;
            siz[x] = siz[x] + siz[y];
            //val[x]=val[x]+val[y];
        }
    }

    bool same(int x, int y) {
        return find(x) == find(y);
    }

    int size(int x) {
        return siz[find(x)];
    }

    int ngroup() {
        //int ngroup( int& ans ) {
        int count = 0;
        int i;
        for (i = 0; i < num; i++) {
            if (par[i] == i) {
                count++;
                //ans += (val[i]? siz[i]: siz[i]-1);
            }
        }
        return count;
    }
};

void solve()
{
    int n, m, s, t;
    scanf("%d%d%d%d", &n, &m, &s, &t); s--; t--;
    vector<int> p(n),a(m),b(m);
    int i,k;
    for (i = 0; i < n; i++) {
        scanf("%d", &p[i]);
    }
    map<int, vector<int>> z;
    for (i = 0; i < m; i++) {
        scanf("%d%d", &a[i], &b[i]); a[i]--; b[i]--;
        int tmp = min(p[a[i]], p[b[i]]);
        z[tmp].push_back(i);
    }
    UF uf(n);
    int ans = 0;
    int pre = 1;
    auto it = z.rbegin();
    for (; it != z.rend(); it++) {
        int tmp = it->first;
        vector<int>& v = it->second;
        for (k = 0; k < (int)v.size(); k++) {
            int id = v[k];
            uf.unite(a[id], b[id]);
        }
        int nn=uf.size(s);
        //printf("%d\n", nn);
        if (pre < nn && tmp < p[s]) {
            ans++;
        }
        pre = nn;

        //if (uf.same(s, t)) break;
    }
    printf("%d\n", ans);

    return;
}

int main()
{
#if 1
    solve();
#else
    int T, t;
    scanf("%d", &T);
    for (t = 0; t < T; t++) {
        //cout << "Case #" << t + 1 << ": ";
        solve();
    }
#endif
    return 0;
}