from collections import defaultdict

*V, n = map(int, input().split())

now = [0] * 4
now[0] = V[0]

idx = defaultdict(lambda : -1)
route = [now[:]]

for i in range(1000000):
    l, r = i % 4, (i + 1) % 4
    move = min(now[l], V[r] - now[r])
    now[l] -= move
    now[r] += move

    tpn = tuple(now)
    if tpn in idx:
        break

    idx[tpn] = i
    route.append(now[:])

loop = idx[tuple(now)] + 1

if n < loop:
    print(route[n])
else:
    route = route[loop:]
    n -= loop
    print(route[n % len(route)])