Buggy python submission (verdict: Runtime Error):
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n):
        for a, b, c in ABC:
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for a, b, c in ABC:
        if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
            return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))


Fixed submission:
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None:
                continue
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None or distance[b - 1] is None:
                continue
            if distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c
                if b == n:
                    return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))

Buggy python submission (verdict: Runtime Error):
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n):
        for a, b, c in ABC:
            if distance[a - 1] is not None and \
                (distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c):
                distance[b - 1] = distance[a - 1] + c

    for a, b, c in ABC:
        if distance[b - 1] < distance[a - 1] + c:
            return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))


Fixed submission:
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None:
                continue
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None or distance[b - 1] is None:
                continue
            if distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c
                if b == n:
                    return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))

Buggy python submission (verdict: Runtime Error):
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n):
        for a, b, c in ABC:
            if distance[a - 1] is not None and
                (distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c):
                distance[b - 1] = distance[a - 1] + c

    for a, b, c in ABC:
        if distance[b - 1] < distance[a - 1] + c:
            return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))


Fixed submission:
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None:
                continue
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None or distance[b - 1] is None:
                continue
            if distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c
                if b == n:
                    return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))

Buggy python submission (verdict: Runtime Error):
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n):
        for a, b, c in ABC:
            if distance[a - 1] is not None and \
                distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for a, b, c in ABC:
        if distance[b - 1] < distance[a - 1] + c:
            return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))


Fixed submission:
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None:
                continue
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None or distance[b - 1] is None:
                continue
            if distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c
                if b == n:
                    return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))

Buggy python submission (verdict: Runtime Error):
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n):
        for a, b, c in ABC:
            if distance[a - 1] is not None and distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for a, b, c in ABC:
        if distance[b - 1] < distance[a - 1] + c:
            return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))


Fixed submission:
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None:
                continue
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None or distance[b - 1] is None:
                continue
            if distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c
                if b == n:
                    return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))

Buggy python submission (verdict: Runtime Error):
def solve(n, m, ABC):
    g = [[] for _ in range(n)]
    for a, b, c in ABC:
        g[a - 1].append((b - 1, c))

    distance = [-10 ** 10] * n
    distance[0] = 0
    parents = [-1] * n
    ng = [False]

    def search(node):
        if ng[0]:
            return
        for to, d in g[node]:
            if node == parents[to] and distance[to] < distance[node] + d:
                ng[0] = True
                return
            if distance[to] < distance[node] + d:
                distance[to] = distance[node] + d
                parents[to] = node
            search(to)

    search(0)
    return 'inf' if ng[0] else distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))


Fixed submission:
def solve(n, m, ABC):
    distance = [None] * n
    distance[0] = 0

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None:
                continue
            if distance[b - 1] is None or distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c

    for _ in range(n - 1):
        for a, b, c in ABC:
            if distance[a - 1] is None or distance[b - 1] is None:
                continue
            if distance[b - 1] < distance[a - 1] + c:
                distance[b - 1] = distance[a - 1] + c
                if b == n:
                    return 'inf'

    return distance[n - 1]

_n, _m = map(int, input().split())
_ABC = [list(map(int, input().split())) for _ in range(_m)]
print(solve(_n, _m, _ABC))