def find_max(num_1, num_2):
       max_val = 0.0

   if (num_1 > num_2):  # if num1 is greater than num2,
      max_val = num_1   # then num1 is the maxVal.
   else:                # Otherwise,
      max_val = num_2   # num2 is the maxVal
   return max_val

max_sum = 0.0

num_a = float(input())
num_b = float(input())
num_y = float(input())
num_z = float(input())

max_sum = sum([max([num_a, num_b]), max([num_y, num_z])])

print('max_sum is:', max_sum)