import sys
input=lambda:sys.stdin.readline().rstrip()
A,B,C,D,E=map(int,input().split())
N=A*(B-C)
price=[D for i in range(N)]
for i in range(1,N):
	price[i]=price[i-1]
	if i%10==9 and price[i-1]>=E:
		price[i]-=E
print(sum(price))