Buggy python submission (verdict: Time Limit Exceeded):
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * 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

        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 len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFind(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.union(a, b)
  
cnt = 0
G = uf.all_group_members()
for i,w in enumerate(List):
  if uf.find(i+1) == uf.find(w):
    cnt += 1
  
print(cnt)

Fixed submission:
class UnionFindTree():
    
    def __init__(self, N):
        self.parent = [-1]*(N+1)
        self.rank = [1]*(N+1)
        self.size = [1]*(N+1)
  
    def find(self, i):
        if self.parent[i] == -1:
            group = i
        else:
            group = self.find(self.parent[i]) 
            self.parent[i] = group
        return group
      
    def unite(self, x, y):
        px = self.find(x)
        py = self.find(y)
        if px != py:
            if self.rank[px] == self.rank[py]: # rank is same
                self.rank[px] += 1
            elif self.rank[px] < self.rank[py]:
                px, py = py, px
                
            self.parent[py] = px
            self.size[px] += self.size[py]
    
    def getsize(self, x):
        return self.size[self.find(x)]
    
    def groups(self, index1=True):
        return set([self.find(i) for i in range(0+index1, N+index1)])
      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFindTree(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.unite(a, b)
  
cnt = 0
for i,w in enumerate(List):
  if uf.find(i+1) == uf.find(w):
    cnt += 1
  
print(cnt)

Buggy python submission (verdict: Time Limit Exceeded):
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * 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

        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 len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFind(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.union(a, b)
  
cnt = 0
G = uf.all_group_members()
for i in range(N):
  a = uf.find(List[i])
  b = G[a]
  if i+1 in b:
    cnt += 1
  
print(cnt)

Fixed submission:
class UnionFindTree():
    
    def __init__(self, N):
        self.parent = [-1]*(N+1)
        self.rank = [1]*(N+1)
        self.size = [1]*(N+1)
  
    def find(self, i):
        if self.parent[i] == -1:
            group = i
        else:
            group = self.find(self.parent[i]) 
            self.parent[i] = group
        return group
      
    def unite(self, x, y):
        px = self.find(x)
        py = self.find(y)
        if px != py:
            if self.rank[px] == self.rank[py]: # rank is same
                self.rank[px] += 1
            elif self.rank[px] < self.rank[py]:
                px, py = py, px
                
            self.parent[py] = px
            self.size[px] += self.size[py]
    
    def getsize(self, x):
        return self.size[self.find(x)]
    
    def groups(self, index1=True):
        return set([self.find(i) for i in range(0+index1, N+index1)])
      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFindTree(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.unite(a, b)
  
cnt = 0
for i,w in enumerate(List):
  if uf.find(i+1) == uf.find(w):
    cnt += 1
  
print(cnt)

Buggy python submission (verdict: Time Limit Exceeded):
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * 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

        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 len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFind(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.union(a, b)
  
cnt = 0
for i in range(N):
  a = uf.find(List[i])
  b = uf.all_group_members()[a]
  if i+1 in b:
    cnt += 1
  
print(cnt)

Fixed submission:
class UnionFindTree():
    
    def __init__(self, N):
        self.parent = [-1]*(N+1)
        self.rank = [1]*(N+1)
        self.size = [1]*(N+1)
  
    def find(self, i):
        if self.parent[i] == -1:
            group = i
        else:
            group = self.find(self.parent[i]) 
            self.parent[i] = group
        return group
      
    def unite(self, x, y):
        px = self.find(x)
        py = self.find(y)
        if px != py:
            if self.rank[px] == self.rank[py]: # rank is same
                self.rank[px] += 1
            elif self.rank[px] < self.rank[py]:
                px, py = py, px
                
            self.parent[py] = px
            self.size[px] += self.size[py]
    
    def getsize(self, x):
        return self.size[self.find(x)]
    
    def groups(self, index1=True):
        return set([self.find(i) for i in range(0+index1, N+index1)])
      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFindTree(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.unite(a, b)
  
cnt = 0
for i,w in enumerate(List):
  if uf.find(i+1) == uf.find(w):
    cnt += 1
  
print(cnt)

Buggy python submission (verdict: Time Limit Exceeded):
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * 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

        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 len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFind(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.union(a, b)
  
cnt = 0
for i in range(N):
  a = uf.find(List[i])
  b = uf.all_group_members()[a]
  if i+1 in b:
    cnt += 1
  
print(cnt)

Fixed submission:
class UnionFindTree():
    
    def __init__(self, N):
        self.parent = [-1]*(N+1)
        self.rank = [1]*(N+1)
        self.size = [1]*(N+1)
  
    def find(self, i):
        if self.parent[i] == -1:
            group = i
        else:
            group = self.find(self.parent[i]) 
            self.parent[i] = group
        return group
      
    def unite(self, x, y):
        px = self.find(x)
        py = self.find(y)
        if px != py:
            if self.rank[px] == self.rank[py]: # rank is same
                self.rank[px] += 1
            elif self.rank[px] < self.rank[py]:
                px, py = py, px
                
            self.parent[py] = px
            self.size[px] += self.size[py]
    
    def getsize(self, x):
        return self.size[self.find(x)]
    
    def groups(self, index1=True):
        return set([self.find(i) for i in range(0+index1, N+index1)])
      
N,M = map(int,input().split())
List=list(map(int,input().split()))

List2=[list(map(int,input().split())) for i in range(M)]
uf = UnionFindTree(N+1)

for i in range(M):
  a = List2[i][0]
  b = List2[i][1]  
  uf.unite(a, b)
  
cnt = 0
for i,w in enumerate(List):
  if uf.find(i+1) == uf.find(w):
    cnt += 1
  
print(cnt)