Connect cities

n, m = [ int(x) for x in input("").split(" ") ]
roads = [ [ int(x)-1 for x in input("").split(" ") ] for _ in range(m) ]

adj: list[list[int]] = [ [] for _ in range(n) ]

for a, b in roads:
    adj[a].append(b)
    adj[b].append(a)

seen: list[bool] = [False] * n

def dfs(x: int):
    if seen[x]:
        return
    seen[x] = True
    for y in adj[x]:
        dfs(y)

path: list[int] = []

for i in range(n):
    if not seen[i]:
        path.append(i)
        dfs(i)

k = len(path) - 1

print(k)
for i in range(k):
    print(f"{path[i]+1} {path[i+1]+1}")

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 24, in <module>
    d...

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 24, in <module>
    d...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 24, in <module>
    d...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 24, in <module>
    d...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 24, in <module>
    d...

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED