# 1453 : 手助け

from sys import stdin

candiesPerPerson,inviting,noComing,price,borderPrice=list(map(int,stdin.readline().split()))
numComing=inviting-noComing
cost=0
candies=candiesPerPerson*numComing
if candies!=0:
    cost+=price
    priceIm1=price
    for i in range(2,candies+1):
        if i%10!=0:
            cost+=priceIm1
        else:
            if priceIm1>=borderPrice:
                cost+=(priceIm1-borderPrice)
                priceIm1-=borderPrice
            else:
                cost+=priceIm1
else:
    cost=0
print(cost)