#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
//#define int long long
using namespace std;

int N, D;

signed main()
{
	cin >> N >> D;

	int now = 1, cnt = 0;
	while (now <= N) {
		now += D;
		cnt++;
	}

	if (now > N + 1) {
		cout << N - 1 << endl;
	} else {
		cout << --cnt << endl;
	}
}