Buggy python submission (verdict: Time Limit Exceeded):
#最小領域木
#ABC065D - Built?
#https://atcoder.jp/contests/abc065/tasks/arc076_b

#自己考察

n = int(input())
lst = [list(map(int,input().split())) for _ in range(n)]
cad = []

for i in range(n):
    for j in range(i,n):
        tmp = min(abs(lst[i][0]-lst[j][0]),abs(lst[i][1]-lst[j][1]))
        cad.append([tmp,i,j])
        
cad.sort()

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())

h = UnionFind(n)
cost = 0
for i in range(len(cad)):
    a = cad[i][1]
    b = cad[i][2]
    c = cad[i][0]
    if  not h.same(a,b):
        h.union(a,b)
        cost += c

print(cost)

Fixed submission:
#最小領域木
#ABC065D - Built?
#https://atcoder.jp/contests/abc065/tasks/arc076_b

#自己考察TLE

import sys

n = int(input())
cad = []
lst = []
for i in range(n):
    x, y =  list(map(int,input().split()))
    lst.append([x,y,i])
lstx = lst.sort(key = lambda x: x[0])
for i in range(n-1):
    cad.append([lst[i+1][0] - lst[i][0],lst[i+1][2],lst[i][2]])
lsty = lst.sort(key = lambda x: x[1])
for i in range(n-1):
    cad.append([lst[i+1][1] - lst[i][1],lst[i+1][2],lst[i][2]])

cad.sort()

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())

h = UnionFind(n)
cost = 0
count = 0
for i in range(len(cad)):
    a = cad[i][1]
    b = cad[i][2]
    c = cad[i][0]
    if  not h.same(a,b):
        h.union(a,b)
        cost += c
        count += 1
    if count == n-1:
        print(cost)
        sys.exit()

Buggy python submission (verdict: Time Limit Exceeded):
#最小領域木
#ABC065D - Built?
#https://atcoder.jp/contests/abc065/tasks/arc076_b

#自己考察

n = int(input())
lst = [list(map(int,input().split())) for _ in range(n)]
cad = []

for i in range(n):
    for j in range(i,n):
        tmp = min(abs(lst[i][0]-lst[j][0]),abs(lst[i][1]-lst[j][1]))
        cad.append([tmp,i,j])
        
cad.sort()

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())

h = UnionFind(n)
cost = 0
for i in range(len(cad)):
    a = cad[i][1]
    b = cad[i][2]
    c = cad[i][0]
    if  not h.same(a,b):
        h.union(a,b)
        cost += c

print(cost)

Fixed submission:
#最小領域木
#ABC065D - Built?
#https://atcoder.jp/contests/abc065/tasks/arc076_b

#自己考察TLE

import sys

n = int(input())
cad = []
lst = []
for i in range(n):
    x, y =  list(map(int,input().split()))
    lst.append([x,y,i])
lstx = lst.sort(key = lambda x: x[0])
for i in range(n-1):
    cad.append([lst[i+1][0] - lst[i][0],lst[i+1][2],lst[i][2]])
lsty = lst.sort(key = lambda x: x[1])
for i in range(n-1):
    cad.append([lst[i+1][1] - lst[i][1],lst[i+1][2],lst[i][2]])

cad.sort()

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())

h = UnionFind(n)
cost = 0
count = 0
for i in range(len(cad)):
    a = cad[i][1]
    b = cad[i][2]
    c = cad[i][0]
    if  not h.same(a,b):
        h.union(a,b)
        cost += c
        count += 1
    if count == n-1:
        print(cost)
        sys.exit()