Buggy python submission (verdict: Time Limit Exceeded):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
ps = make_ps(50000)
while True:
    n = int(input())
    if not n:
        break
    if n % 2:
        print(1 if n - 2 in ps else 0)
    else:
        res = 0
        for p in ps:
            if p > n / 2:
                break
            if n - p in ps:
                res += 1
        print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)

Buggy python submission (verdict: Time Limit Exceeded):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
ps = make_ps(50000)
while True:
    n = int(input())
    if not n:
        break
    if n % 2:
        print(1 if n - 2 in ps else 0)
    else:
        res = 0
        for p in ps:
            if p > n / 2:
                break
            if n - p in ps:
                res += 1
        print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)

Buggy python submission (verdict: Time Limit Exceeded):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
while True:
    n = int(input())
    ps = make_ps(n)
    if not n:
        break
    if n % 2:
        print(1 if n - 2 in ps else 0)
    else:
        res = 0
        for p in ps:
            if p > n / 2:
                break
            if n - p in ps:
                res += 1
        print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)

Buggy python submission (verdict: Time Limit Exceeded):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
while True:
    n = int(input())
    ps = make_ps(n)
    if not n:
        break
    if n % 2:
        print(1 if n - 2 in ps else 0)
    else:
        res = 0
        for p in ps:
            if p > n / 2:
                break
            if n - p in ps:
                res += 1
    print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)

Buggy python submission (verdict: Runtime Error):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
ps = make_ps(n)
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if n - 2 in ps:
            res += 1
    else:
        res = 0
        for p in ps:
            if p > n / 2:
                break
            if n - p in ps:
                res += 1
    print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)

Buggy python submission (verdict: Time Limit Exceeded):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
ps = make_ps(50000)
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if n - 2 in ps:
            res += 1
    else:
        res = 0
        for p in ps:
            if p > n / 2:
                break
            if n - p in ps:
                res += 1
    print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)

Buggy python submission (verdict: Time Limit Exceeded):
def make_ps(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return [i for i in range(n) if tbl[i]]
ps = make_ps(50000)
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if n - 2 in ps:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if n - p in ps:
                res += 1
    print(res)

Fixed submission:
def make_tbl(n):
    tbl = [False, True, False, False, False, True] * (n // 6 + 1)
    for i in range(1, 4):
        tbl[i] = not tbl[i]
    p, stp, sqrt = 5, 2, n ** 0.5
    while p < sqrt:
        for i in range(p ** 2, n, 2 * p):
            tbl[i] = False
        while True:
            p += stp
            stp = 6 - stp
            if tbl[p]:
                break
    return tbl
tbl = make_tbl(50000)
ps = [i for i in range(50000) if tbl[i]]
while True:
    n = int(input())
    if not n:
        break
    res = 0
    if n % 2:
        if tbl[n - 2]:
            res += 1
    else:
        res = 0
        for p in ps:
            if 2 * p > n:
                break
            if tbl[n - p]:
                res += 1
    print(res)