import sys,bisect,string,math,time,functools,random,fractions from heapq import heappush,heappop,heapify from collections import deque,defaultdict,Counter from itertools import permutations,combinations,groupby rep=range def Golf():n,*t=map(int,open(0).read().split()) def I():return int(input()) def S_():return input() def IS():return input().split() def LS():return [i for i in input().split()] def MI():return map(int,input().split()) def LI():return [int(i) for i in input().split()] def LI_():return [int(i)-1 for i in input().split()] def NI(n):return [int(input()) for i in range(n)] def NI_(n):return [int(input())-1 for i in range(n)] def StoLI():return [ord(i)-97 for i in input()] def ItoS(n):return chr(n+97) def LtoS(ls):return ''.join([chr(i+97) for i in ls]) def RA():return map(int,open(0).read().split()) def GI(V,E,ls=None,Directed=False,index=1): org_inp=[];g=[[] for i in R(V)] FromStdin=True if ls==None else False for i in R(E): if FromStdin: inp=LI() org_inp.append(inp) else: inp=ls[i] if len(inp)==2: a,b=inp;c=1 else: a,b,c=inp if index==1:a-=1;b-=1 aa=(a,c);bb=(b,c);g[a].append(bb) if not Directed:g[b].append(aa) return g,org_inp def GGI(h,w,search=None,replacement_of_found='.',mp_def={'#':1,'.':0},boundary=1): #h,w,g,sg=GGI(h,w,search=['S','G'],replacement_of_found='.',mp_def={'#':1,'.':0},boundary=1) # sample usage mp=[boundary]*(w+2);found={} for i in R(h): s=input() for char in search: if char in s: found[char]=((i+1)*(w+2)+s.index(char)+1) mp_def[char]=mp_def[replacement_of_found] mp+=[boundary]+[mp_def[j] for j in s]+[boundary] mp+=[boundary]*(w+2) return h+2,w+2,mp,found def TI(n):return GI(n,n-1) def accum(ls): rt=[0] for i in ls:rt+=[rt[-1]+i] return rt def bit_combination(n,base=2): rt=[] for tb in R(base**n):s=[tb//(base**bt)%base for bt in R(n)];rt+=[s] return rt def gcd(x,y): if y==0:return x if x%y==0:return y while x%y!=0:x,y=y,x%y return y def YN(x):print(['NO','YES'][x]) def Yn(x):print(['No','Yes'][x]) def show(*inp,end='\n'): if show_flg:print(*inp,end=end) mo=10**9+7 inf=float('inf') FourNb=[(-1,0),(1,0),(0,1),(0,-1)];EightNb=[(-1,0),(1,0),(0,1),(0,-1),(1,1),(-1,-1),(1,-1),(-1,1)];compas=dict(zip('WENS',FourNb));cursol=dict(zip('LRUD',FourNb)) l_alp=string.ascii_lowercase #sys.setrecursionlimit(10**7) read=sys.stdin.buffer.read;readline=sys.stdin.buffer.readline;input=lambda:sys.stdin.readline().rstrip() show_flg=False show_flg=True class Comb: def __init__(self,n,mo=10**9+7): self.fac=[0]*(n+1) self.inv=[1]*(n+1) self.fac[0]=1 self.fact(n) for i in range(1,n+1): self.fac[i]=i*self.fac[i-1]%mo self.inv[n]*=i self.inv[n]%=mo self.inv[n]=pow(self.inv[n],mo-2,mo) for i in range(1,n): self.inv[n-i]=self.inv[n-i+1]*(n-i+1)%mo return def fact(self,n): return self.fac[n] def invf(self,n): return self.inv[n] def comb(self,x,y): if y<0 or y>x: return 0 return self.fac[x]*self.inv[x-y]*self.inv[y]%mo n,k=LI() a=LI() ans=0 c=[1]*n for i in range(1,n): c[i]=c[i-1]*(k+i)*pow(i,mo-2,mo)%mo for i in range(n): l=i+1 r=n-i ans+=a[i]*c[i]*c[n-1-i] ans%=mo print(ans)