mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    def f(n, m):
        ret = 0
        for i in range(1, 100):
            x = n // (m ** i)
            if x == 0:
                break
            ret += x
        return ret

    N, K, M = map(int, input().split())
    print(f(N, M) - f(K, M) - f(N - K, M))


if __name__ == '__main__':
    main()