Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return {i for i in range(self.n) if self.root(i) == root}

    def all_roots(self):
        return {i for i, x in enumerate(self.parents) if x < 0}

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = uf.members(r)
        member = {p[l]-1 for l in loop}
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = set(uf.members(r))
        member = {p[l]-1 for l in loop}
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = uf.members(r)
        member = {p[l]-1 for l in loop}
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for i, (a,b) in enumerate(ab):
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)


ans = 0

for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = uf.members(r)
        member = set()
        for l in loop:
            member.add(p[l]-1)
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for i, (a,b) in enumerate(ab):
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)


ans = 0

for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = uf.members(r)
        member = set()
        for l in loop:
            member.add(p[l]-1)
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for i, (a,b) in enumerate(ab):
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)


ans = 0

for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = uf.members(r)
        member = []
        for l in loop:
            member.append(p[l]-1)
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for i, (a,b) in enumerate(ab):
    a,b = a-1,b-1
    uf.union(a,b)


ans = 0
for r in uf.all_roots():
    if uf.size(r) == 1:
        if p[r]-1 == r: ans += 1
    else:
        loop = uf.members(r)
        member = []
        for l in loop:
            member.append(p[l]-1)
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for i, (a,b) in enumerate(ab):
    a,b = a-1,b-1
    uf.union(a,b)


ans = 0
visited = [0]*n
for i in range(len(p)):
    if visited[p[i]-1] == 1:
        continue

    if uf.size(p[i]-1) == 1:
        if p[i]-1 == i: ans += 1
        visited[i]==1
    else:
        loop = uf.members(p[i]-1)
        visited[i]=1
        member = []
        for l in loop:
            member.append(p[l]-1)
            visited[l] = 1
        ans += len(set(loop) & set(member))

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for i, (a,b) in enumerate(ab):
    a,b = a-1,b-1
    uf.union(a,b)


ans = 0
visited = [0]*n
for i in range(len(p)):
    if visited[p[i]-1] == 1:
        continue

    if uf.size(p[i]-1) == 1:
        if p[i]-1 == i: ans += 1
        visited[i]==1
    else:
        loop = uf.members(p[i]-1)
        visited[i]=1
        for l in loop:
            if p[l]-1 in loop:ans += 1
            visited[l] = 1

print(ans)


Fixed submission:

import sys
sys.setrecursionlimit(10 ** 7)
input = sys.stdin.readline

n, m = map(int, input().split())
p = list( map(int, input().split()))

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def root(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.root(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.root(x)
        y = self.root(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.root(x)]

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

    def members(self, x):
        root = self.root(x)
        return [i for i in range(self.n) if self.root(i) == root]

    def all_roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.all_roots())

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

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

uf = UnionFind(n)
ab = [tuple(map(int,input().split())) for i in range(m)]
for a,b in ab:
    a,b = a-1,b-1
    if uf.is_same(a,b): continue
    uf.union(a,b)

ans = 0

loop = [set() for i in range(n)]
for i in range(n):
    r = uf.root(i)
    loop[r].add(i)

for i in range(n):
    for j in loop[i]:
        if p[j]-1 in loop[i]: ans += 1

print(ans)