Количество минут, которое Кот либо пел песню и при этом шёл направо, либо рассказывал сказку и при этом шёл налево

P, S, K = map(int, input().split())
T = int(input())
 
num_periods = T // (2 * K)
 
time_in_periods = num_periods * (P + S)
 
remaining_time = T - num_periods * 2 * K
 
if remaining_time <= K:
    time_in_remaining_period = P * (remaining_time % K)
else:
    time_in_remaining_period = P + S * ((remaining_time - K) % K)
 
total_time = time_in_periods + time_in_remaining_period
 
print(total_time)

P, S, K = map(int, input().split())
T = int(input())
 
num_periods = (T + K) // (2 * K)
 
time_in_periods = num_periods * (P + S)
 
remaining_time = T - num_periods * 2 * K
 
if remaining_time <= K:
    time_in_remaining_period = P * (remaining_time % K)
else:
    time_in_remaining_period = P + S * ((remaining_time - K) % K)
 
total_time = time_in_periods + time_in_remaining_period
 
print(total_time)

P, S, K = map(int, input().split())
T = int(input())
 
num_periods = max(1, T // (2 * K))
 
time_in_periods = num_periods * (P + S)
 
remaining_time = T - num_periods * 2 * K
 
if remaining_time <= K:
    time_in_remaining_period = P * (remaining_time % K)
else:
    time_in_remaining_period = P + S * ((remaining_time - K) % K)
 
total_time = time_in_periods + time_in_remaining_period
 
print(total_time)

P, S, K = map(int, input().split())
T = int(input())
 
if T >= K:
    period_length = K
else:
    period_length = T
 
num_periods = T // (2 * K)
total_period_length = num_periods * (P + S)
 
remainder = T % (2 * K)
if remainder < period_length:
    total_period_length += remainder
else:
    total_period_length += period_length + (remainder - period_length) // 2 * (P + S)
 
print(total_period_length)

from itertools import count
# input = open('input.txt').readline
p, s, k = map(int, input().split())
t = int(input())
 
def spans(len, start, end):
    return zip(count(start, len), count(end, len))
 
def sizes_of_intersects(*spans, limit):
    spans = [[0, 0, s] for s in spans]
    while True:
        s1 = max(spans, key=lambda s: s[0])
        s2 = min(spans, key=lambda s: s[1])
        a, b = s1[0], s2[1]
        if a >= limit: break
        if b >= limit: yield t - a; break
        if a < b: yield b - a
        s2[0], s2[1] = next(s2[2])
 
go_right, go_left = spans(2*k, 0, k), spans(2*k, k, 2*k)
songs, tales = spans(p+s, 0, p), spans(p+s, p, p+s)
s1 = sum(sizes_of_intersects(go_right, songs, limit=t))
s2 = sum(sizes_of_intersects(go_left, tales, limit=t))
print(s1 + s2)