Buggy python submission (verdict: Runtime Error):
# coding:utf-8

K, A, B = [int(i) for i in input().split()]

def cal(K, A, B):
    BNUM = 1
    TRANS_GET = B - A
    # 操作開始
    counter = 0
    while counter < K:
        nokori = K - counter
        if BNUM >= A:
        # 交換可能
            if nokori >= 2:
                syou = int(nokori / 2)
                amari = nokori % 2
                BNUM += TRANS_GET * syou + amari
                break
            else:
                BNUM += nokori
                break
        else:
        # 交換不可
            atonanko = A - BNUM
            if atonanko < nokori-2:
                BNUM += atonanko
                counter += atonanko
            else:
                BNUM += nikori
                break
    return BNUM


if A < B:
    if B - A > 2:
        max_b = cal(K, A, B)
    else:
        max_b = 1 + K
else:
    max_b = 1 + K

print(max_b)

Fixed submission:
# coding:utf-8

K, A, B = [int(i) for i in input().split()]

def cal(K, A, B):
    BNUM = 1
    TRANS_GET = B - A
    # 操作開始
    counter = 0
    while counter < K:
        nokori = K - counter
        if BNUM >= A:
        # 交換可能
            if nokori >= 2:
                syou = int(nokori / 2)
                BNUM += TRANS_GET * syou
                counter += syou * 2
            else:
                # 叩く
                BNUM += 1
                counter += 1
        else:
        # 交換不可
            atonanko = A - BNUM
            if atonanko <= nokori-2:
                BNUM += atonanko
                counter += atonanko
            else:
                BNUM += nokori
                break
    return BNUM


if B - A <= 2:
    max_b = 1 + K
else:
    max_b = cal(K, A, B)

print(max_b)

Buggy python submission (verdict: Runtime Error):
# coding:utf-8

K, A, B = [int(i) for i in input().split()]
print(K, A, B)

def cal(K, A, B):
    BNUM = 1
    TRANS_GET = B - A
    # 操作開始
    counter = 0
    while counter < K:
        nokori = K - counter
        if BNUM >= A:
        # 交換可能
            if nokori >= 2:
                BNUM += TRANS_GET
                counter += 2
            else:
                BNUM += nokori
                break
        else:
        # 交換不可
            atonanko = A - BNUM
            if atonanko < nokori-2:
                BNUM += atonanko
                counter += atonanko
            else:
                BNUM += nikori
                break
    return BNUM


if A < B:
    if B - A > 2:
        max_b = cal(K, A, B)
    else:
        max_b = 1 + K
else:
    max_b = 1 + K

print(max_b)

Fixed submission:
# coding:utf-8

K, A, B = [int(i) for i in input().split()]

def cal(K, A, B):
    BNUM = 1
    TRANS_GET = B - A
    # 操作開始
    counter = 0
    while counter < K:
        nokori = K - counter
        if BNUM >= A:
        # 交換可能
            if nokori >= 2:
                syou = int(nokori / 2)
                BNUM += TRANS_GET * syou
                counter += syou * 2
            else:
                # 叩く
                BNUM += 1
                counter += 1
        else:
        # 交換不可
            atonanko = A - BNUM
            if atonanko <= nokori-2:
                BNUM += atonanko
                counter += atonanko
            else:
                BNUM += nokori
                break
    return BNUM


if B - A <= 2:
    max_b = 1 + K
else:
    max_b = cal(K, A, B)

print(max_b)