def main():
    NS = int(input())
    EW = int(input())
    v = int(input())

    ans = abs(NS//v)
    if not(NS%v==0):ans += 1

    ans = abs(ans + EW//v)
    if not(EW%v==0):ans += 1
    if not( NS == 0 and EW == 0 ):ans += 1
    print(ans)

if __name__=="__main__":
    main()