#include <stdio.h>
#include<vector>
#include <algorithm>
#include <map>
using namespace std;
typedef long long ll;
const int MX = 105, MM = 1000000007;
ll rv(ll A){
ll R = 1, B = MM-2;
while(B){
if( B&1 ) R = R * A % MM;
A = A * A % MM; B /= 2;
}
return R;
}
struct frac{
ll A, B;
frac(ll A):A(A), B(1){}
frac(ll a, ll b){
A = (a%MM+MM) % MM;
B = (b%MM+MM) % MM;
}
frac(){A = 0, B = 1;}
frac operator+ (const frac &l)const{
return frac((A * l.B + B * l.A) % MM, B * l.B % MM);
}
frac operator*(const frac &l)const{
return frac(A*l.A % MM, B*l.B % MM);
}
frac operator/(const frac &l)const{
return frac(A*l.B % MM, B*l.A % MM);
}
frac operator- (const frac &l)const{
return frac((A*l.B - B*l.A%MM + MM) % MM, B*l.B % MM);
}
ll v(){ return A * rv(B) % MM; }
};
int main()
{
int N, KK;
scanf("%d%d", &N, &KK);
frac tot = 0;
for(int K = KK+1; K <= N; K++){
frac ans = 0, mul = 1;
for(int i = 1; i <= N; i++){
mul = mul * i;
}
for(int i = N; i >= 1; i--){
mul = mul / i;
ans = ans + mul * (N-i+1);
mul = mul * (i-K);
}
ans = ans * K * (N-K+1);
tot = ans + tot;
}
printf("%lld\n", tot.v());
}
