06.Fishland

skumriq_price = float(input())
caca_price = float(input())
palamud_kg = float(input())
safrid_kg = float(input())
midi_kg = int(input())

palamud_price = skumriq_price + skumriq_price * 0.6
palamud_sum = palamud_kg * palamud_price
safrid_price = caca_price + caca_price * 0.8
safrid_sum = safrid_kg * safrid_price
midi_sum = midi_kg * 7.50

total_sum = palamud_sum + safrid_sum + midi_sum
print(round(total_sum, 2))