#include<bits/stdc++.h>
using namespace std;
#define ll long long
void toggle(ll I,vector<bool>&arr,ll K){
    
    for(ll i=I-1,k=K-1;i>=0 && i<arr.size() && k>=0;i--,k--)
        arr[i] = true ^ arr[i];
    for(ll i=I,k=K;i<arr.size() && k>=0;i++,k--)
        arr[i] = true ^ arr[i];
}
ll solve(ll I,vector<ll>&cost,ll n,vector<bool> curr,ll k){
    if(I>=n){
        for(int i=0;i<curr.size();i++)
            if(curr[i])
                return INT_MAX;
        return 0;
    }
    toggle(I,curr,k);
    ll toggleCost = solve(I+1,cost,n,curr,k);
    toggle(I,curr,k);
    ll unToggleCost = solve(I+1,cost,n,curr,k);
    return (toggleCost>unToggleCost)?1:0+min(toggleCost,unToggleCost);
}
int main(){
    ll n,k; cin >> n,k;
    vector<ll> arr(n);
    vector<bool> curr(n,false);
    cout<<solve(0,arr,n,curr,k)<<endl;
    return 0;
}