Connect cities

def find_minimum_roads(n, m, roads):
    adj = [[] for _ in range(n + 1)]
    for a, b in roads:
        adj[a].append(b)
        adj[b].append(a)
    visited = [False] * (n + 1)
    
    def dfs(city):
        visited[city] = True
        for neighbor in adj[city]:
            if not visited[neighbor]:
                dfs(neighbor)
    components = []
    for city in range(1, n + 1):
        if not visited[city]:
            components.append(city)
            dfs(city)
    if len(components) == 1:
        print(0)
        return
    
    print(len(components) - 1)
    
    for i in range(1, len(components)):
        print(components[i - 1], components[i])

n, m = map(int, input().split())
roads = [tuple(map(int, input().split())) for _ in range(m)]

# Finding and printing the result
find_minimum_roads(n, m, roads)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 31, in <module>
    f...

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 31, in <module>
    f...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 31, in <module>
    f...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 31, in <module>
    f...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 31, in <module>
    f...

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED