Connect cities

x = input()
n = x.split(" ")[0]
m = x.split(" ")[1]
n = int(n)
m = int(m)

roads = []
for _ in range(m):
    x = input()
    roads.append([int(x.split(" ")[0]), int(x.split(" ")[1])])

buckets = []


for idx, road in enumerate(roads):
    a = road[0]
    b = road[1]
    i = 0
    while i < len(buckets):
        bucket = buckets[i]
        if a in bucket:
            buckets[i].append(b)
            j = i + 1
            while j < len(buckets):
                bucket_2 = buckets[j]
                if b in bucket_2:
                    bucket[i] = bucket[i].extend(bucket_2)
                    buckets.remove(bucket_2)
                    break
                j += 1
        elif b in bucket:
            buckets[i].append(a)
            j = i + 1
            while j < len(buckets):
                bucket_2 = buckets[j]
                if a in bucket_2:
                    bucket.extend(bucket_2)
                    buckets.remove(bucket_2)
                    break
                j += 1
        elif idx - 1 == len(buckets) - 1:
            buckets.append([a, b])

        i += 1
    
    if len(buckets) == 0:
        buckets.append([a, b])




print(len(buckets) - 1)
i = 0
while i <= len(buckets) - 2:
    bucket = buckets[i]
    bucket_1 = buckets[i + 1]
    print(f"{bucket[0]} {bucket_1[0]}")
    i += 1

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
AttributeError: 'int' object has no attribute 'extend'

Test 3

Verdict: ACCEPTED

Test 4

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
AttributeError: 'int' object has no attribute 'extend'

Test 5

Verdict: ACCEPTED

Test 6

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
IndexError: list index out of range

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
IndexError: list index out of range

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
IndexError: list index out of range

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
IndexError: list index out of range

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 27, in <module>
    bucket[i] = bucket[i].extend(bucket_2)
IndexError: list index out of range

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER