Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
path = []
ans = 0
ap = path.append
for i in range(N):
    A = int(input())
    ap([])
    for j in range(A):
        x, y = map(int,input().split())
        x -= 1
        path[-1].append((x, y))
for i in range(1<<N):
    i |= (1<<N)
    judge = True
    for j in range(N):
        if (1<<j) & i:
            for k in range(len(path[j])):
                if path[j][k][1] != int(bin(i)[-path[j][k][0] - 1]):
                    judge = False
    if judge:
        if ans < bin(i).count("1") - 1:
            ans = bin(i).count("1") - 1
print(ans)

Fixed submission:
N = int(input())
path = []
ans = 0
for i in range(N):
    A = int(input())
    path.append([])
    for j in range(A):
        x, y = map(int,input().split())
        x -= 1
        path[-1].append((x, y))
for i in range(1<<N):
    i |= (1<<N)
    judge = True
    for j in range(N):
        if not judge:
            break
        if (1<<j) & i:
            for k in range(len(path[j])):
                if path[j][k][1] != int(bin(i)[-path[j][k][0] - 1]):
                    judge = False
                    break
    if judge:
        if ans < bin(i).count("1") - 1:
            ans = bin(i).count("1") - 1
print(ans)

Buggy python submission (verdict: Runtime Error):
N = int(input())
path = []
ans = 0
ap = path.append
Ap = path[-1].append
for i in range(N):
    A = int(input())
    ap([])
    for j in range(A):
        x, y = map(int,input().split())
        x -= 1
        Ap((x, y))
for i in range(1<<N):
    i |= (1<<N)
    judge = True
    for j in range(N):
        if (1<<j) & i:
            for k in range(len(path[j])):
                if path[j][k][1] != int(bin(i)[-path[j][k][0] - 1]):
                    judge = False
    if judge:
        if ans < bin(i).count("1") - 1:
            ans = bin(i).count("1") - 1
print(ans)

Fixed submission:
N = int(input())
path = []
ans = 0
for i in range(N):
    A = int(input())
    path.append([])
    for j in range(A):
        x, y = map(int,input().split())
        x -= 1
        path[-1].append((x, y))
for i in range(1<<N):
    i |= (1<<N)
    judge = True
    for j in range(N):
        if not judge:
            break
        if (1<<j) & i:
            for k in range(len(path[j])):
                if path[j][k][1] != int(bin(i)[-path[j][k][0] - 1]):
                    judge = False
                    break
    if judge:
        if ans < bin(i).count("1") - 1:
            ans = bin(i).count("1") - 1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
path = []
ans = 0
for i in range(N):
    A = int(input())
    path.append([])
    for j in range(A):
        x, y = map(int,input().split())
        x -= 1
        path[-1].append((x, y))
for i in range(1<<N):
    i |= (1<<N)
    judge = True
    for j in range(N):
        if (1<<j) & i:
            for k in range(len(path[j])):
                if path[j][k][1] != int(bin(i)[-path[j][k][0] - 1]):
                    judge = False
    if judge:
        if ans < bin(i).count("1") - 1:
            ans = bin(i).count("1") - 1
print(ans)

Fixed submission:
N = int(input())
path = []
ans = 0
for i in range(N):
    A = int(input())
    path.append([])
    for j in range(A):
        x, y = map(int,input().split())
        x -= 1
        path[-1].append((x, y))
for i in range(1<<N):
    i |= (1<<N)
    judge = True
    for j in range(N):
        if not judge:
            break
        if (1<<j) & i:
            for k in range(len(path[j])):
                if path[j][k][1] != int(bin(i)[-path[j][k][0] - 1]):
                    judge = False
                    break
    if judge:
        if ans < bin(i).count("1") - 1:
            ans = bin(i).count("1") - 1
print(ans)