//#pragma GCC target ("avx")
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<random>
#include<functional>
#include<algorithm>
#include<stack>
#include<cstdio>
#include<cstring>
#include<bitset>
#include<unordered_map>
#include<climits>
#include<fstream>
#include<complex>
#include<time.h>
#include<cassert>
#include<functional>
#include<numeric>
#include<tuple>
using namespace std;
using ll = long long;
using ld = long double;
using H = pair<ll, ll>;
using P = pair<ll, H>;
using vi = vector<ll>;
#define all(a) (a).begin(),(a).end()
#define fs first
#define sc second
#define xx first
#define yy second.first
#define zz second.second
#define Q(i,j,k) mkp((i),mkp((j),(k)))
#define rng(i,s,n) for(ll i = (s) ; i < (n) ; i++)
#define rep(i,n) rng(i, 0, (n))
#define mkp make_pair
#define vec vector
#define pb emplace_back
#define siz(a) int((a).size())
#define crdcomp(b) sort(all((b)));(b).erase(unique(all((b))),(b).end())
#define getidx(b,i) (lower_bound(all((b)),(i))-(b).begin())
#define ssp(i,n) (i==(ll)(n)-1?"\n":" ")
#define ctoi(c) (int)((c)-'0')
#define itoc(c) (char)((c)+'0')
#define cyes printf("Yes\n")
#define cno printf("No\n")
#define cdf(n) for(int quetimes_=(n);quetimes_>0;quetimes_--)
#define gcj printf("Case #%lld: ",quetimes_+1)
#define readv(a,n) (a).resize((n),0);rep(i,(n)) (a)[i]=read()
#define found(a,x) (a.find(x)!=a.end())
constexpr ll mod = (ll)1e9 + 7;
constexpr ll Mod = 998244353;
constexpr ld EPS = 1e-10;
constexpr ll inf = (ll)3 * 1e18;
constexpr int Inf = (ll)15 * 1e8;
constexpr int dx[] = { -1,1,0,0 }, dy[] = { 0,0,-1,1 };
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
ll read() { ll u, k = scanf("%lld", &u); return u; }
string reads() { string s; cin >> s; return s; }
H readh(short g = 0) { H u; int k = scanf("%lld %lld", &u.fs, &u.sc); if (g == 1) u.fs--, u.sc--; if (g == 2) u.fs--; return u; }
bool ina(H t, int h, int w) { return 0 <= t.fs && t.fs < h && 0 <= t.sc && t.sc < w; }
bool ina(int t, int l, int r) { return l <= t && t < r; }
ll gcd(ll i, ll j) { return j ? gcd(j, i % j) : i; }
ll ppc(ll x) {
    int sum = 0; for (int i = 0; i < 60; i++)if ((1ll << i) & x) sum++;
    return sum;
}
template<typename T>
void fin(T x) { cout << x << endl; exit(0); }

template<typename T>
class csum {
    vec<T> v;
public:
    csum(vec<T>& a) :v(a) { build(); }
    csum() {}
    csum(int sz) { init(sz); }
    void init(int sz) { v = vector<T>(sz + 1, 0); }
    void init(vec<T>& a) { v = a; build(); }
    void build() {
        for (int i = 1; i < v.size(); i++) v[i] += v[i - 1];
    }
    void add(int l, int r, T x) {
        v[l] += x;
        v[r] -= x;
    }//[l,r)
    void add(int t, T x) {
        v[t] += x;
    }//[l,r)
    //[l,r]
    T a(int l, int r) {
        if (r < l) return 0;
        return v[r] - (l == 0 ? 0 : v[l - 1]);
    }
    //[l,r)
    T b(int l, int r) {
        return a(l, r - 1);
    }
    T a(pair<int, int>t) {
        return a(t.first, t.second);
    }
    T b(pair<int, int>t) {
        return b(t.first, t.second);
    }
    T operator[](int x)const {
        return v[x];
    }
};
template<ll mod>
class modint {
public:ll v;
      modint(ll v = 0) { s(v % mod + mod); }
      constexpr static int fn_ = (ll)2e6 + 5;
      static vector<modint>fact, comp;
      modint pow(ll x) const {
          modint b(v), c(1);
          while (x) {
              if (x & 1) c *= b;
              b *= b;
              x >>= 1;
          }
          return c;
      }
      inline modint& s(int vv) {
          v = vv < mod ? vv : vv - mod;
          return *this;
      }
      inline modint inv()const { return pow(mod - 2); }
      inline modint operator-()const { return modint() - *this; }
      inline modint& operator+=(const modint b) { return s(v + b.v); }
      inline modint& operator-=(const modint b) { return s(v + mod - b.v); }
      inline modint& operator*=(const modint b) { v = v * b.v % mod; return *this; }
      inline modint& operator/=(const modint b) { v = v * b.inv().v % mod; return *this; }
      inline modint operator+(const modint& b) const { return modint(v) += b; }
      inline modint operator-(const modint& b) const { return modint(v) -= b; }
      inline modint operator*(const modint& b) const { return modint(v) *= b; }
      inline modint operator/(const modint& b) const { return modint(v) /= b; }
      friend ostream& operator<<(ostream& os, const modint& m) {
          return os << m.v;
      }
      friend istream& operator>>(istream& is, modint& m) {
          int x; is >> x; m = modint(x);
          return is;
      }
      bool operator<(const modint& r)const { return v < r.v; }
      bool operator>(const modint& r)const { return v > r.v; }
      bool operator<=(const modint& r)const { return v <= r.v; }
      bool operator>=(const modint& r)const { return v >= r.v; }
      bool operator==(const modint& r)const { return v == r.v; }
      bool operator!=(const modint& r)const { return v != r.v; }
      explicit operator bool()const { return v; }
      explicit operator int()const { return v; }
      modint comb(modint k) {
          if (k > *this) return modint();
          if (fact.empty()) combinit();
          if (v >= fn_) {
              if (k > *this - k) k = *this - k;
              modint tmp(1);
              for (int i = v; i >= v - k.v + 1; i--) tmp *= modint(i);
              return tmp * comp[k.v];
          }
          return fact[v] * comp[k.v] * comp[v - k.v];
      }//nCk
      modint perm(modint k) {
          if (k > *this) return modint();
          if (fact.empty()) combinit();
          if (v >= fn_) {
              modint tmp(1);
              for (int i = v; i >= v - k.v + 1; i--) tmp *= modint(i);
              return tmp;
          }
          return fact[v] * comp[v - k.v];
      }//nPk
      static void combinit() {
          fact.assign(fn_, modint());
          fact[0] = 1;
          for (int i = 1; i < fn_; i++) fact[i] = fact[i - 1] * modint(i);
          comp.assign(fn_, modint());
          comp[fn_ - 1] = fact[fn_ - 1].inv();
          for (int i = fn_ - 2; i >= 0; i--) comp[i] = comp[i + 1] * modint(i + 1);
      }
};
using mint = modint<ll(1e9 + 7)>; template<>vec<mint> mint::fact = vec<mint>(); template<>vec<mint> mint::comp = vec<mint>();
//--------------------------------------------------------------
template<typename T>
class BIT {
    int size;
    vector<T>dat;
public:
    BIT() {}
    BIT(vector<T>v) {
        init(v);
    }
    BIT(int n) { init(n); }
    void init(int n) {
        size = n;
        dat.assign(size + 1, 0);
    }
    void init(vector<T>v) {
        init(v.size());
        for (int i = 1; i <= size; i++) {
            dat[i] += v[i - 1];
            if (i + (i & -i) <= size) dat[i + (i & -i)] += dat[i];
        }
    }
    void add(int i, ll x) {
        i++;
        while (i <= size) {
            chmax(dat[i], x);
            i += i & -i;
        }
    }
    void change(int i, ll x) {
        i++; int t = x - dat[i];
        while (i <= size) {
            int k = dat[i];
            dat[i] += t;
            t = dat[i] - k;
            i += i & -i;
        }
    }
    //[l,r)
    void add(int l, int r, ll x) {
        add(l, x); add(r, -x);
    }
    //[0,i]
    T query(int i) {
        i++;
        T sum = 0;
        while (i > 0) {
            chmax(sum, dat[i]);
            i -= i & -i;
        }
        return sum;
    }
    //[l,r)
    T query(int l, int r) {
        return query(r - 1) - query(l - 1);
    }
    //[0,x) >= w
    int lower_bound(T w) {
        if (w <= 0) return 0;
        int x = 0, k = 1;
        while (k * 2 < size) k *= 2;
        for (; k > 0; k /= 2) {
            if (x + k <= size && dat[x + k] < w) {
                w -= dat[x + k];
                x += k;
            }
        }
        return x;
    }
};//size, 0-indexed
class unionfind {
    int size = 0, grps = 0;
    vector<int>pa;
public:
    unionfind() {}
    unionfind(int n) {
        init(n);
    }
    void init(int n) {
        size = n, grps = n;
        pa.assign(n, -1);
    }
    int root(int x) {
        if (pa[x] < 0) return x;
        return pa[x] = root(pa[x]);
    }
    bool unite(int x, int y) {
        x = root(x); y = root(y);
        if (x == y) return false;
        grps--;
        if (pa[x] > pa[y]) swap(x, y);
        pa[x] += pa[y];
        pa[y] = x;
        return true;
    }
    bool same(int x, int y) {
        return root(x) == root(y);
    }
    bool isroot(int x) {
        return x == root(x);
    }
    int sz(int x) {
        return -pa[root(x)];
    }
    int groups() {
        return grps;
    }
    H operator[](int x) {
        x = root(x);
        return H{ x,-pa[x] };
    }
};
//--------------------------------------------------------------
int n, m, s, t;
vi e[200000];
signed main() {
    cin >> n >> m >> s >> t;
    s--; t--;
    vi a; readv(a, n);
    unionfind uf(n);
    rep(i, m) {
        int u, v; cin >> u >> v;
        u--; v--;
        uf.unite(u, v);
    }
    vi b;
    rep(i, n) if (uf.same(i, s)) b.pb(a[i]);
    crdcomp(b);
    cout << getidx(b, a[s]) << endl;
}