#include <bits/stdc++.h>

using namespace std;

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

typedef long long int64;

int main()
{
  int64 N, K;
  cin >> N >> K;
  if(K >= N) {
    cout << 0 << endl;
  } else if(K == 1) {
    cout << (N + 1) / 2 << endl;
  } else {
    int64 call = N / (K + 1);
    N -= call * (K + 1);
    if(N >= K) cout << call << endl;
    else cout << call + 1 << endl;
  }
}