n, x, t = map(int, input().split())
c = 0
for i in range(n):
    n = n - x
    c = c + t
    if n <= 0:
        print(c)
        break

ca99122c7f832585a7865ee157eadc9b270884ba
<mask token>

<mask token>
for i in range(n):
    n = n - x
    c = c + t
    if n <= 0:
        print(c)
        break

n, x, t = map(int, input().split())
c = 0
for i in range(n):
    n = n - x
    c = c + t
    if n <= 0:
        print(c)
        break
