#pragma region template
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
 
using ll=long long;
using ld=long double;
using vi=vector<int>;
using vll=vector<ll>;
using pi=pair<int,int>;
using pll=pair<ll,ll>;
 
#define overload2(a,b,c,...) c
#define overload3(a,b,c,d,...) d
#define overload4(a,b,c,d,e,...) e
#define overload5(a,b,c,d,e,f,...) f
 
#define TYPE1(T) template<typename T>
#define TYPE2(T,U) template<typename T,typename U>
#define TYPE(...) overload2(__VA_ARGS__,TYPE2,TYPE1)(__VA_ARGS__)
#define TYPES1(T) template<typename... T>
#define TYPES2(H,T) template<typename H,typename... T>
#define TYPES(...) overload2(__VA_ARGS__,TYPES2,TYPES1)(__VA_ARGS__)
 
#define REP4(i,s,n,d) for(int i=(s);i<(n);i+=(d))
#define REP3(i,s,n) REP4(i,s,n,1)
#define REP2(i,n) REP3(i,0,n)
#define REP1(n) REP2(tomato,n)
#define REP(...) overload4(__VA_ARGS__,REP4,REP3,REP2,REP1)(__VA_ARGS__)
 
#define RREP4(i,n,s,d) for(int i=(n)-1;i>=s;i-=d)
#define RREP3(i,n,s) RREP4(i,n,s,1)
#define RREP2(i,n) RREP3(i,n,0)
#define RREP1(n) RREP2(tomato,n)
#define RREP(...) overload4(__VA_ARGS__,RREP4,RREP3,RREP2,RREP1)(__VA_ARGS__)

#define FOR4(a,b,c,d,v) for(auto [a,b,c,d]:v)
#define FOR3(a,b,c,v) for(auto [a,b,c]:v)
#define FOR2(a,b,v) for(auto [a,b]:v)
#define FOR1(a,v) for(auto a:v)
#define FOR(...) overload5(__VA_ARGS__,FOR4,FOR3,FOR2,FOR1)(__VA_ARGS__)

#define AFOR4(a,b,c,d,v) for(auto&[a,b,c,d]:v)
#define AFOR3(a,b,c,v) for(auto&[a,b,c]:v)
#define AFOR2(a,b,v) for(auto&[a,b]:v)
#define AFOR1(a,v) for(auto&a:v)
#define AFOR(...) overload5(__VA_ARGS__,AFOR4,AFOR3,AFOR2,AFOR1)(__VA_ARGS__)

#define CFOR4(a,b,c,d,v) for(const auto&[a,b,c,d]:v)
#define CFOR3(a,b,c,v) for(const auto&[a,b,c]:v)
#define CFOR2(a,b,v) for(const auto&[a,b]:v)
#define CFOR1(a,v) for(const auto&a:v)
#define CFOR(...) overload5(__VA_ARGS__,CFOR4,CFOR3,CFOR2,CFOR1)(__VA_ARGS__)
 
#define ALL(v) v.begin(),v.end()
#define RALL(v) v.rbegin(),v.rend()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(RALL(v))
#define REVERSE(v) reverse(ALL(v))
#define UNIQUE(v) SORT(v),v.erase(unique(ALL(v)),v.end())
 
TYPES(T) void input(T&... a){ (cin>>...>>a); }
#define DECLARE(T,...) T __VA_ARGS__;input(__VA_ARGS__);
#define INT(...) DECLARE(int,__VA_ARGS__)
#define STR(...) DECLARE(string,__VA_ARGS__)
#define LL(...) DECLARE(long long,__VA_ARGS__)
#define CHR(...) DECLARE(char,__VA_ARGS__)
#define DBL(...) DECLARE(double,__VA_ARGS__)
#define VI(n,v) vi v(n);cin>>v;
#define VLL(n,v) vll v(n);cin>>v;
 
TYPE(T) istream&operator>>(istream&is,vector<T>&v){
  for(auto&a:v)cin>>a;
  return is;
}
TYPE(T) ostream&operator<<(ostream&os,const vector<T>&v){
  if(&os==&cerr)os<<"[";
  REP(i,v.size()){
    os<<v[i];
    if(i+1<v.size())os<<(&os==&cerr?",":" ");
  }
  if(&os==&cerr)os<<"]";
  return os;
}
TYPE(T,S) istream&operator>>(istream&is,pair<T,S>&p){
  cin>>p.first>>p.second;
  return is;
}

#ifdef __LOCAL
 #include <debug>
#else
 #define debug(...) void(0)
#endif

void print(){ cout << '\n'; }
TYPES(T,Ts) void print(const T& a,const Ts&... b){
  cout<<a;
  (cout<<...<<(cout<< ' ',b));
  cout << '\n';
}
 
TYPE(T) using pq=priority_queue<T>;
TYPE(T) using pqg=priority_queue<T,vector<T>,greater<T>>;
TYPE(T) T pick(queue<T>& que){assert(que.size()); T a=que.front();que.pop();return a;}
TYPE(T) T pick(pq<T>& que){assert(que.size()); T a=que.top();que.pop();return a;}
TYPE(T) T pick(pqg<T>& que){assert(que.size()); T a=que.top();que.pop();return a;}
TYPE(T) T pick(stack<T>& sta){assert(sta.size()); T a=sta.top();sta.pop();return a;}
 
string YES(bool f=true){return (f?"YES":"NO");}
string Yes(bool f=true){return (f?"Yes":"No");}
string yes(bool f=true){return (f?"yes":"no");}
 
constexpr int INF=1e9+7;
constexpr ll LINF=ll(1e18)+7;
constexpr ld EPS=1e-10;
 
vi iota(int n){vi a(n);iota(ALL(a),0);return a;}
TYPE(T) vector<pair<T,int>> query_sort(const vector<T>&v){
  vector<pair<T,int>> res(v.size());
  REP(i,v.size())res[i]={v[i],i};
  SORT(res);
  return res;
}
TYPE(T) T rev(T a){ REVERSE(a);return a; }
TYPE(T) void fin(T a){cout<<a<<endl;exit(0);}
TYPE(T) bool chmax(T &a,T b){return (a<b&&(a=b,true));}
TYPE(T) bool chmin(T &a,T b){return (a>b&&(a=b,true));}
TYPES(T,Ns) auto make_vector(T x,int n,Ns ...ns){
  if constexpr(sizeof...(ns)==0)return vector<T>(n,x);
  else return vector(n,make_vector<T>(x,ns...));
}
bool in(const ll S,const int a){return (S>>a)&1;}
int popcount(const ll S){return __builtin_popcountll(S);}
int digit(char c){ return (c>='0' and c<='9' ? c-'0' : -1);}
#pragma endregion template

#include <atcoder/modint>
using namespace atcoder;
using mint=modint1000000007;
ostream& operator<<(ostream &os,mint a){os<<a.val();return os;}
istream& operator>>(istream &is,mint &a){
  long long b;is>>b;a=b;
  return is;
}
template<class Monoid>
class SegmentTree{
  using X=typename Monoid::value_type;
  vector<X> dat;
  int n,log,size;

  void update(int i){ dat[i]=Monoid::op(dat[2*i],dat[2*i+1]); }
public:
  SegmentTree():SegmentTree(0){}
  SegmentTree(int n):SegmentTree(vector<X>(n, Monoid::unit())){}
  SegmentTree(vector<X> v):n(v.size()){
    for(log=1;(1<<log)<n;log++){}
    size=1<<log;
    dat.assign(size<<1,Monoid::unit());
    for (int i=0;i<n;++i)dat[size+i]=v[i];
    for (int i=size-1;i>=1;--i) update(i);
  }

  X operator[](int i)const{ return dat[size+i]; }

  void set(int i,const X&x){
    assert(0<=i and i<n);
    dat[i+=size]=x;
    while(i>>=1)update(i);
  }
  void multiply(int i,const X&x){ set(i,Monoid::op(dat[i+size],x));}

  X prod(int L,int R)const{
    assert(0<=L and L<=R and R<=n);
    X vl=Monoid::unit(),vr=Monoid::unit();
    L+=size, R+=size;
    while(L<R){
      if(L&1)Monoid::Rchop(vl,dat[L++]);
      if(R&1)Monoid::Lchop(dat[--R],vr);
      L>>=1,R>>=1;
    }
    return Monoid::op(vl,vr);
  }
  X prod_all()const{ return dat[1]; }

  template <class F>
  int max_right(F& check,int L){
    assert(0<=L && L<=n && check(Monoid::unit()));
    if(L == n) return n;
    L += size;
    X sm = Monoid::unit();
    do {
      while (L % 2 == 0) L >>= 1;
      if (!check(Monoid::op(sm, dat[L]))) {
        while (L < size) {
          L <<= 1;
          if (check(Monoid::op(sm, dat[L])))
            Monoid::Rchop(sm, dat[L++]);
        }
        return L - size;
      }
      Monoid::Rchop(sm, dat[L++]);
    } while ((L & -L) != L);
    return n;
  }

  template <class F>
  int min_left(F& check, int R) {
    assert(0 <= R && R <= n && check(Monoid::unit()));
    if (R == 0) return 0;
    R += size;
    X sm = Monoid::unit();
    do {
      --R;
      while (R > 1 && (R % 2)) R >>= 1;
      if (!check(Monoid::op(dat[R], sm))) {
        while (R < size) {
          ( R <<= 1 )++;
          if (check(Monoid::op(dat[R], sm)))
            Monoid::Lchop(dat[R--], sm);
        }
        return R + 1 - size;
      }
      Monoid::Lchop(dat[R], sm);
    } while ((R & -R) != R);
    return 0;
  }

  X Xor_prod(int l, int r, int xor_val) {
    assert(Monoid::commute);
    X x = Monoid::unit();
    for (int k = 0; k < log + 1; ++k) {
      if (l >= r) break;
      if (l & 1) { Monoid::Rchop(x, dat[(size >> k) + ((l++) ^ xor_val)]); }
      if (r & 1) { Monoid::Rchop(x, dat[(size >> k) + ((--r) ^ xor_val)]); }
      l /= 2, r /= 2, xor_val /= 2;
    }
    return x;
  }

  ostream& operator<<(ostream&os)const{
    os<<"(";
    for(int L=1;L<=size;L<<=1){
      os<<"[";
      for(int j=L;j<(L<<1);j++){
        os<<dat[j];
        if(j+1<(L<<1))os<<",";
      }
      os<<"]";
    }
    os<<")";
    return os;
  }
};
template<typename X>
struct GroupAdd {
  using value_type = X;
  static constexpr X op(const X &x, const X &y) noexcept { return x + y; }
  static constexpr void Rchop(X&x, const X&y){ x+=y; }
  static constexpr void Lchop(const X&x, X&y){ y+=x; }
  static constexpr X inverse(const X &x) noexcept { return -x; }
  static constexpr X power(const X &x, long long n) noexcept { return X(n) * x; }
  static constexpr X unit() { return X(0); }
  static constexpr bool commute = true;
};

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  INT(n,l);
  SegmentTree<GroupAdd<mint>> seg(n+1);
  seg.set(0,1);
  for(int i=1;i<=n;i++){
    int L=max(0,i-l);
    seg.set(i,seg.prod(L,i));
  }
  cout<<seg[n]<<endl;
}