import times, strutils, sequtils, math, algorithm, tables, sets, lists, intsets
import critbits, future, strformat, deques
template `max=`(x,y) = x = max(x,y)
template `min=`(x,y) = x = min(x,y)
template `mod=`(x,y) = x = x mod y
template scan2 = (scan(), scan())
template scan3 = (scan(), scan())
let read* = iterator: string {.closure.} =
    while true: (for s in stdin.readLine.split: yield s)
proc scan(): int = read().parseInt
proc scanf(): float = read().parseFloat
proc toInt(c:char): int =
    return int(c) - int('0')

proc xgcd(a,b:int):(int,int,int)=
  var
    b = b
    x0=1
    y0=0
    x1=0
    y1=1
    q:int
    a = a
  while b!=0:
    (q,a,b) = (a.div(b),b,a.mod(b))
    (x0,x1)=(x1,x0-q*x1)
    (y0,y1)=(y1,y0-q*y1)
  return (a,x0,y0)

# modの逆元
proc modinv(a,m:int):int=
  var (g,x,y)=xgcd(a,m)
  if g!=1:
    return -1
  else:
    return ((x mod m) + m).mod(m)



proc solve():int=
  var
    n = scan()
    k = scan()
    a = newseqwith(n,scan())
    md = 10^9+7
    comb = newseqwith(n+1,0)
  comb[0]=1 # combination(k,0)
  for idx in 1..n:
    var
      tk = k+idx
      tv = idx
    comb[idx] = ((comb[idx-1]*tk).mod(md)*modinv(tv,md)).mod(md)
  #echo comb
  for i in 0..<n:
    result+=((comb[i]*a[i]).mod(md)*(comb[n-i-1])).mod(md)
  result.mod=md
  
    
  
  

  

  
echo solve()