A,B,C,D,E = map(int,input().split())

guest = B-C
candy = A*(B-C)

ans = 0
cost = D
for i in range(candy):
    if i == 0:
        ans += cost
    else:
        cost = cost-E if i%10 == 0 and E <= cost else cost 
        ans += cost
print(ans)