def matrix_power(A,p):
  temp=A
  bench=p-1
  ret=A
  while bench>0:
    if bench%2:
      ret=matrix_product(ret,temp)
    bench=bench//2
    temp=matrix_product(temp,temp)
  return ret

def matrix_product(A,B):
  ret=[[0 for i in range(len(B[0]))] for i in range(len(A))]
  for i in range(len(A)):
    for j in range(len(B[0])):
      s=0
      for k in range(len(A[i])):
          s+=A[i][k]*B[k][j]
      ret[i][j]=s
  return ret
  
n,c=map(int,input().split())
a=list(map(int,input().split()))
A=[[0 for i in range(n)] for i in range(n)]
b=[[1] for i in range(n)]
for i in range(n):
    for j in range(i+1):
        A[i][j]=a[j]
ans=matrix_product(matrix_power(A,c),b)[n-1][0]
for i in range(n):
    ans-=a[i]**c
print(ans)