import sys
readline = sys.stdin.readline

class UnionFind(object):
    def __init__(self, n=1):
        self.par = [i for i in range(n)]
        self.rank = [0 for _ in range(n)]
        self.size = [1 for _ in range(n)]

    def find(self, x):
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                x, y = y, x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
            self.par[y] = x
            self.size[x] += self.size[y]

    def is_same(self, x, y):
        return self.find(x) == self.find(y)

    def get_size(self, x):
        x = self.find(x)
        return self.size[x]
    

N, M, S, T = map(int, readline().split())
S, T = S - 1, T - 1
P = list(map(int, readline().split()))
U = UnionFind(N)
for i in range(M):
    A, B = map(int, readline().split())
    A, B = A - 1, B - 1
    U.union(A, B)

SS = set()
for i in range(N):
    if U.find(i) != U.find(S):
        continue
    if P[i] < P[S]:
        SS.add(P[i])

print(len(SS))