Connect cities

# Get the number of cities and roads
n,m = [int(i) for i in input().split()]

connections = [[0] * n for _ in range(n)]
for i in range(n):
    connections[i][i] = 1

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

for repeat in range(n):
    for i in range(n):
        for j in range(n):
            for k in range(n):
                if connections[i][j]*connections[j][k] == 1:
                    connections[i][k] = 1
                    connections[k][i] = 1
# print(connections)

groups = set()
for i in range(n):
    group = tuple(connections[i])
    groups.add(group)

print(len(groups)-1)

origin = groups.pop()
origin_n = 0
for i,g in enumerate(origin):
    if g == 1:
        origin_n = i+1
        break
while groups:
    group = groups.pop()
    group_n = 0
    for i,g in enumerate(group):
        if g == 1:
            group_n = i+1
            break
    print(origin_n,group_n)

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

Test 7

Verdict: RUNTIME ERROR

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR

Test 11

Verdict: RUNTIME ERROR

Test 12

Verdict: ACCEPTED