Longest route

import math

def dfs(v, d):
    global g, visited, depth, goto, n
    # print(v)
    if v == n - 1:
        depth[v] = 0
        visited[v] = True
        # print(depth[v])
        return
    for w in g[v]:
        if not visited[w]:
            dfs(w, d + 1)
        if 1 + depth[w] > depth[v]:
            depth[v] = 1 + depth[w]
            goto[v] = w
    visited[v] = True


n, m = map(int, input().split())
visited = [False] * n
depth = [-math.inf] * n
goto = [-1] * n
g = [[] for _ in range(n)]
for i in range(m):
    a, b = map(int, input().split())
    g[a - 1].append(b - 1)

#paths = [None for _ in range(n)]
# print(paths)
#
# print(g)
#path = find_path(0, n - 1)
dfs(0, 0)
# print(*depth)
# print(*goto)

if depth[0] > -1:
    print(depth[0] + 1)
    print(1, end=" ")
    v = goto[0]
    while v != -1:
        print(v + 1, end=" ")
        v = goto[v]
else:
    print('IMPOSSIBLE')

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: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 34, in <module>
    dfs(0,...

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 34, in <module>
    dfs(0,...

Test 16

Verdict: ACCEPTED

Test 17

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 34, in <module>
    dfs(0,...

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 34, in <module>
    dfs(0,...

Test 21

Verdict: ACCEPTED