Course Schedule

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

req = []
state=[0 for _ in range(n)]
sol =[]
for i in range(n):
    req.append([])
    
for i in range(m):
    a,b=[int(x) for x in input().split()]
    req[a-1].append(b-1)

i=0
def search(node):
    state[node]=1
    for neigh in req[node]:
        if state[neigh] == 0:
            if not(search(neigh)):
                return False
        elif state[neigh]== 1:
            return False
    state[node]=2
    sol.append(node)
    return True
flag = True
while i<n:
    if state[i]==0:
        if search(i) == False:
            print("IMPOSSIBLE")
            flag = False
            break
    i+=1
if flag:
    print(" ".join(str(x+1) for x in sol[::-1]))

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

Test 13

Verdict: ACCEPTED

Test 14

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 28, in <module>
    if search(i) == False:
  File "input/code.py", line 18, in search
    if not(search(neigh)):
  File "input/code.py", line 18, in search
    if not(search(neigh)):
  File "input/code.py", line 18, in search
    if not(search(neigh)):
  [Previous line repeated 1576 more times]
  File "input/code.py", line 15, in search
    state[node]=1
RecursionError: maximum recursion depth exceeded

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED