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

#define rep(i, n) for(int i = 0; i < (n); i++)
#define repp(i, l, r) for(int i = (l); i < (r); i++)
#define per(i, n) for(int i = ((n)-1); i >= 0; i--)
#define perr(i, l, r) for(int i = ((r)-1); i >= (l); i--)
#define all(x) (x).begin(),(x).end()
#define MOD 1000000007
#define IINF 1000000000
#define LINF 1000000000000000000
#define SP <<" "<<
#define CYES cout<<"Yes"<<endl
#define CNO cout<<"No"<<endl
#define CFS cin.tie(0);ios::sync_with_stdio(false)

typedef long long LL;
typedef long double LD;

int l,k;

int dfs(int x){
  if(x<0) return 0;
  return 1+dfs(x-2)+dfs(x-k-1);
}

int main(){
  cin >> l >> k;
  vector<LL> a(100,0);
  LL ans=0;
  a[0]=1,a[k-1]=1;
  repp(i,0,l){
    if(i>=2) a[i]+=a[i-2];
    if(i>=k+1) a[i]+=a[i-k-1];
    ans+=a[i];
  }
  cout << ans << endl;
  return 0;
}

