#include <bits/stdc++.h>
using namespace std;
template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  for (T i : v) os << i << ' ';
  return os;
}
template <class T>
ostream& operator<<(ostream& os, const set<T>& v) {
  for (T i : v) os << i << ' ';
  return os;
}
template <class T, class S>
ostream& operator<<(ostream& os, const pair<T, S>& v) {
  os << v.first << ' ' << v.second;
  return os;
}
template <class T, class S>
ostream& operator<<(ostream& os, const unordered_map<T, S>& v) {
  for (auto i : v) os << '(' << i.first << "=>" << i.second << ')' << ' ';
  return os;
}
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target( \
    "avx2,sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
const long long inf = 1e18;
const long long mod = 1e9 + 7;
void fast() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
}
clock_t time_p = clock();
void starboy1299() {
  time_p = clock() - time_p;
  cerr << "Time Taken : " << (float)(time_p) / CLOCKS_PER_SEC << "\n";
}
const long long N = 5e5 + 5;
void solve() {
  long long n, p;
  cin >> n >> p;
  for (long long i = 1; i <= 32; i++) {
    long long val = n - p * i;
    long long temp = __builtin_popcount(val);
    if (temp <= i and val >= i) {
      cout << i << '\n';
      return;
    }
  }
  cout << -1 << '\n';
}
int32_t main() {
  fast();
  long long t = 1;
  for (long long i = 1; i <= t; i++) {
    solve();
  }
  starboy1299();
}
