a, b, c, d, e = map(int, input().split())
num = b - c
now = d
if num == 0:
    exit(print(0))
ans = d
for i in range(1, num):
    if (i + 1) % 10 != 0: ans += now
    else:
        if e <= now: now -= e; ans += now
        else: ans += now
print(ans)