#include #include #include #include #include #include #include #include #include #include #include #include #include #pragma warning(disable:4996) typedef long long ll; #define MIN(a, b) ((a)>(b)? (b): (a)) #define MAX(a, b) ((a)<(b)? (b): (a)) #define LINF 9223300000000000000 #define INF 2140000000 const long long MOD = 1000000007; using namespace std; int main(int argc, char* argv[]) { int n, p; scanf("%d%d", &n, &p); assert(n>=2); vector a(n+1); ll ans=0, sum=0; int i; for(i=1; i<=n; i++) { if(i==1) a[i]=0; else if(i==2) a[i]=1; else a[i]=(a[i-2]+p*a[i-1])%MOD; sum=(sum+a[i])%MOD; ans=(ans+sum*a[i])%MOD; } printf("%lld\n", ans); return 0; }