#include <cstdio>
#include <vector>
#include <map>
#include <algorithm>
#include <cmath>

#define rep(i,N) for(int (i)=0;(i)<(N);(i)++)

using namespace std;

int main(){
	long int N, K;
	scanf("%u %u", &N, &K);
	for (long int i = ceil((N-K)/(K+1)); i < N/2+2; i++) {
		if (i > (long int) floor((N - i) / K)) {
			printf("%d", i);
			return 0;
		}
	}
	return 0;
}