n,p=map(int,input().split())
A=[0,1]
i=2
while i<=n:
  a=p*A[i-1]+A[i-2]
  A.append(a)
  i+=1

sum1=0
for i in range(n):
  s=A[i]*(sum(A[0+i:n]))
  sum1+=s
print(sum1%1000000007)