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

if __name__ == "__main__":
    main()