Longest route

import sys
sys.setrecursionlimit(10**6)

def find_path(s, f, visited=None):
    global g, n

    path = [s]
    if s == f:
        paths[s] = path
        return path

    max_path = None
    res_path = None
    for w in g[s]:
        # print(w)
        if paths[w] and len(paths[w]) > 0:
            res_path = paths[w]
            if res_path and (not max_path or len(res_path) > len(max_path)):
                max_path = res_path
        elif paths[w]:
            pass
        else:
            res_path = find_path(w, f)
            if res_path and (not max_path or len(res_path) > len(max_path)):
                max_path = res_path

    if max_path:
        path.extend(max_path)
        paths[s] = path
    else:
        paths[s] = []
    # print('mp', max_path, res_path)
    return path


n, m = map(int, input().split())
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)
# print(paths)
if path[-1] != n - 1:
    print('IMPOSSIBLE')
else:
    print(len(path))
    for i in range(len(path)):
        path[i] += 1
    print(*path)

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: TIME LIMIT EXCEEDED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: TIME LIMIT EXCEEDED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: TIME LIMIT EXCEEDED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: TIME LIMIT EXCEEDED

Test 21

Verdict: ACCEPTED