#include <stdio.h>

long long count(long long N, long long M)
{
	long long X, ans = 0;
	for (X = M; 1; X *= M) {
		ans += N / X;
		if (X > N / M) break;
	}
	return ans;
}

int main()
{
	long long N, K, M;
	scanf("%lld %lld %lld", &N, &K, &M);
	printf("%lld\n", count(N, M) - count(N - K, M) - count(K, M));
	fflush(stdout);
	return 0;
}