Building Teams

import sys 

def solve():
    input = sys.stdin.read().split()

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

    adj = [[]for _ in range(n+1)]

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

    team = [0] *(n+1)

    for i in range(1, n + 1): 
        if team[i] == 0: 
            team[i] = 1
            stack = [i]
            while stack: 
                node = stack.pop()
                for neighbor in adj[node]:
                    if team[neighbor] == 0: 
                        team[neighbor] = 3 - team[node]
                        stack.append(neighbor)
                    elif team[neighbor] == team[node]:
                        print('IMPOSSIBLE')
                        return
    
    for i in range(1,len(team)):
        print(team[i], end =' ')

    
if __name__ == '__main__' :
    solve()

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