#yuki978
import sys
n,p=map(int,raw_input().split())
mod=10**9+7
a1,a2=0,1
res=1
temp=1
if n<=2:
 print(n-1)
 sys.exit()
for i in range(2,n):
 a1,a2=a2,(a2*p+a1)%mod
 temp=(temp+a2)%mod
 res=(res+a2*temp)%mod
print(res)