Connect cities

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

for _ in range(m):
    a, b = map(int, input().split())
    adj[a - 1].append(b - 1)
    adj[b - 1].append(a - 1)

components = []
visited = [False for _ in range(n)]
comp = []


def dfs(s):
    if visited[s]:
        return
    visited[s] = True
    comp.append(s)
    for u in adj[s]:
        dfs(u)


for i in range(n):
    if not visited[i]:
        comp = []
        dfs(i)
        components.append(comp)


print(len(components) - 1)
for i in range(1, len(components)):
    print(components[i - 1][0] + 1, components[i][0] + 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 26, in <module>
    d...

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 26, in <module>
    d...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 26, in <module>
    d...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 26, in <module>
    d...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "/box/input/code.py", line 26, in <module>
    d...

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED