import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
import time
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines
write=sys.stdout.write
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
#sys.set_int_max_str_digits(10**9)

W,Z,B=readline().split()
W=int(W)
Z=int(Z)
if B=="0.5":
    ans=(W+Z)*15//10
elif B=="0.8":
    ans=(W+Z)*18//10
elif B=="1.2":
    ans=(W+Z)*22//10
elif B=="1.6":
    ans=(W+Z)*26//10
elif B=="2.0":
    ans=(W+Z)*30//10
print(ans)