#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll N, K;
bool check(ll x) {
	if(N - x <= 0) return true;
	ll rem = N - x;
	return rem < (long double)x * K;
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	cin >> N >> K;

	ll ng = 0, ok = N;
	while(abs(ng - ok) > 1) {
		ll mid = (ng + ok) / 2;
		if(check(mid)) ok = mid;
		else ng = mid;
	}
	cout << ok << endl;
}