#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); vector a(n+1); ll sum=0; int i,j; 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; for(j=1; j<=i; j++) { sum = (sum+(a[i]*a[j]))%MOD; } } printf("%lld\n", sum); return 0; }