Longest route

import sys
sys.setrecursionlimit(10**9)

n, m = [int(x) for x in input().split()]

matrice = {i:set() for i in range(1, n+1)}
for _ in range(m):
    a, b = [int(x) for x in input().split()]
    matrice[a].add(b)

res = [(float('-inf'),-1) for _ in range(n+1)]
visited = set()
def dfs(node):
    if node == n:
        res[node] = (1, "")
        return 1
    for next_node in matrice[node]:
        if next_node in visited:
            length = res[next_node][0] + 1
        else:
            length = dfs(next_node) + 1
        if length > res[node][0]:
            res[node] = (length, next_node)
    visited.add(node)
    return res[node][0]

total_length = dfs(1)
if res[-1] == (-1, -1):
    print("IMPOSSIBLE")
else:
    print(total_length)
    node = 1
    while node != n:
        print(node, end=' ')
        node = res[node][1]
    print(n)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: TIME LIMIT EXCEEDED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: TIME LIMIT EXCEEDED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED