class UnionFind: def __init__(self, n): self.n = n self.parents = [-1] * n self.group = n def find(self, x): if self.parents[x] < 0: return x else: self.parents[x] = self.find(self.parents[x]) return self.parents[x] def union(self, x, y): x = self.find(x) y = self.find(y) if x == y: return self.group -= 1 if self.parents[x] > self.parents[y]: x, y = y, x self.parents[x] += self.parents[y] self.parents[y] = x def size(self, x): return -self.parents[self.find(x)] def same(self, x, y): return self.find(x) == self.find(y) def members(self, x): root = self.find(x) return [i for i in range(self.n) if self.find(i) == root] def roots(self): return [i for i, x in enumerate(self.parents) if x < 0] def group_count(self): return self.group def all_group_members(self): dic = {r:[] for r in self.roots()} for i in range(self.n): dic[self.find(i)].append(i) return dic def __str__(self): return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots()) n, m, s, t = map(int, input().split()) P = list(map(int, input().split())) s -= 1 t -= 1 edges = [[] for _ in range(n)] for _ in range(m): a, b = map(int, input().split()) a -= 1 b -= 1 if P[a] > P[b]: a, b = b, a edges[a].append(b) dic = {} for i, p in enumerate(P): if p not in dic: dic[p] = [] dic[p].append(i) ans = 0 UF = UnionFind(n) for p in sorted(dic.keys(), reverse = True): flg = False tmp = [] for u in dic[p]: for v in edges[u]: if UF.same(v, s): flg = True if flg: ans += 1 for u in dic[p]: for v in edges[u]: UF.union(u, v) print(ans)