Connect cities

n,m = [int(x) for x in input().split()]
voisin = []
for i in range (n):
    voisin.append([])
atteignable = [False for i in range(n)]
atteignable[0] = True

a_visiter = [0]

for i in range (m):
    a,b = [int(x)-1 for x in input().split()]
    voisin[a].append(b)
    voisin[b].append(a)

def visite_ville():
    while a_visiter:
        ville = a_visiter.pop()
        atteignable[ville]=True
        for city in voisin[ville]:
            if atteignable[city] == False:
                a_visiter.append(city)

visite_ville()

i = 1
chemin_a_creer = []
while i<n:
    if atteignable[i] == False:
        a_visiter.append(i)
        visite_ville()
        chemin_a_creer.append("1 "+ str(i+1))
    i+=1
    

print(len(chemin_a_creer))
for elmt in chemin_a_creer:
    print(elmt)

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