Connect cities

import sys

def main():
    input_data = sys.stdin.read().split()
    if not input_data:
        return

    n = int(input_data[0])
    m = int(input_data[1])

    adj = [[] for _ in range(n + 1)]
    idx = 2
    for _ in range(m):
        u = int(input_data[idx])
        v = int(input_data[idx + 1])
        adj[u].append(v)
        adj[v].append(u)
        idx += 2

    visited = [False] * (n + 1)
    representatives = []
    stack = []

    for i in range(1, n + 1):
        if not visited[i]:
            representatives.append(i)
            stack.append(i)

            while stack:
                curr = stack.pop()
                visited[curr] = True
                for neighbor in adj[curr]:
                    if not visited[neighbor]:
                        stack.append(neighbor)

    k = len(representatives) - 1
    print(k)

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

if __name__ == '__main__':
    main()

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED