M=10**9+7;F=[1];Q=[r=0];P=->a,n=M-2{a.pow(n,M)};N,K=gets.split.map &:to_i;a=N
1.upto(K+1){|i|a=a*(N-i)%M;Q<<(P[i,K]+Q[-1])%M;F<<i*F[-1]%M}
N<=K+1&&(p Q[N];exit)
0.upto(K+1){|i|
r=(r+Q[i]*a*P[N-i]*P[F[K+1-i]*F[i]]*[-1,1][(i+K)%2])%M
}
p r