//#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include <iostream>
#include <vector>
#include <set>
#include <array>
#include <cmath>
#include <algorithm>
#include <map>
using namespace std;
#define MAX_INT 2147483647
#define ll long long
int main(){
    int n, p;
    cin >> n >> p;
    if (p >= n){
        cout << -1 << '\n';
        return 0;
    }
    if(p == 0){
        int ans = 0;
        while(n>0){
            ans += (int)n%2;
            n/=2;
        }
        cout << ans << '\n';
    }else{
        for(int i = 1; n - p*i > 0 && n-p*i < 1'000'000'000 ; ++i){
            int temp = n - p*i;
            int cnt_min = 0;
            int cnt_max = 0;
            int bin = 0;
            while(temp > 0){
                cnt_min += (int)temp % 2;
                if(temp%2 == 0){
                    cnt_max += bin;
                    bin = 0;
                }else {
                    bin = (bin * 2) + 1;
                }
                temp/=2;
            }
            cnt_max+= bin;
            if(cnt_min <= i && i <= cnt_max){
                cout << i << '\n';
                return 0;
            }
        }
        cout << -1 << '\n';
    }
    return 0;
}