R=range

def rec_str(a):
	if not isinstance(a,list):return str(a)
	return "".join(["[",", ".join(rec_str(x)for x in a),"]"])
class BIT:
	def __init__(self,x):
		if isinstance(x,int):
			self.N=x
			self.F=[0]*(x+1)
		else:
			self.N=len(x)
			self.F=[0]*(self.N+1)
			for j in R(1,self.N+1):
				i=j-1
				self.F[j]=x[i]
				k=j-(j&-j)
				while i>k:
					self.F[j]+=self.F[i]
					i-=i&-i
	def Add(self,i,u):
		i+=1
		while i<=self.N:
			self.F[i]+=u
			i+=i&-i
	def InitialSegmentSum(self,r):
		assert(r>-2)
		a=0
		i=min(r+1,self.N)
		while i:
			a+=self.F[i]
			i-=i&-i
		return a
class IntervalAddBIT:
	def __init__(self,N):
		self.N=N
		self.F=BIT(N+1)
		self.G=BIT(N+1)
	def IntervalAdd(self,l,r,u):
		self.F.Add(l,-(l-1)*u)
		self.F.Add(r+1,r*u)
		self.G.Add(l,u)
		self.G.Add(r+1,-u)
	def Add(self,i,u):
		self.IntervalAdd(i,i,u)
	def Set(self,i,u):
		self.Add(i,u-self.Get(i))
	def InitialSegmentSum(self,r):
		return self.F.InitialSegmentSum(r)+r*self.G.InitialSegmentSum(r)
	def IntervalSum(self,l,r):
		return self.InitialSegmentSum(r)-self.InitialSegmentSum(l-1)
	def Get(self,i):
		return self.IntervalSum(i,i)
	def list(self):
		return[self.Get(i)for i in R(self.N)]
	def __str__(self):
		return rec_str(self.list())

N,L=map(int,input().split())
P=10**9+7
bit=IntervalAddBIT(N+1)
bit.Add(0,1);
for i in R(N):bit.IntervalAdd(i+1,i+L,bit.Get(i)%P)
print(bit.Get(N)%P)