<gh_stars>0
# Console Entry
N = float(input())
M = float(input())
N_kg = int(input())
M_kg = int(input())
# Formula
income = ((N * N_kg) + (M * M_kg)) / 1.94
# Console Exit
print(income)
# Console Entry
N = float(input())
M = float(input())
N_kg = int(input())
M_kg = int(input())
# Formula
income = ((N * N_kg) + (M * M_kg)) / 1.94
# Console Exit
print(income)
# Console Entry # Formula # Console Exit