def main():
    A, B, C, D, E = map(int, input().split())
    ans = 0
    y = D
    for i in range(1, B - C + 1):
        if i == 1:
            ans += y * A
            continue
        if i % 10 != 0:
            ans += y * A
        else:
            if E <= y:
                ans += (y - E) * A
                y -= E
            else:
                ans += y * A
    print(ans)


if __name__ == "__main__":
    main()