#include <bits/stdc++.h>
#define gibon ios::sync_with_stdio(false); cin.tie(0);
#define bp __builtin_popcount
#define fir first
#define sec second
#define pii pair<int, int>
#define pll pair<ll, ll>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
using namespace std;
int dx[4]={0, 1, 0, -1}, dy[4]={1, 0, -1 , 0};
const int mxN=100010;
const int mxM=350;
const int mxK=350;
const ll MOD=1000000007;
const ll INF=100000000000001;
int N, K;
ll fact[mxN], ifact[mxN];
ll ans;
ll mypow(ll a, ll b)
{
if(b==0) return 1;
if(b==1) return a%MOD;
ll tmp=mypow(a, b/2);
tmp=(tmp*tmp)%MOD;
if(b%2) tmp=(a*tmp)%MOD;
return tmp;
}
int main()
{
gibon
cin >> N >> K; K--;
fact[0]=1; ifact[0]=1;
for(int i=1;i<=N+1;i++) fact[i]=(fact[i-1]*i)%MOD;
for(int i=1;i<=N+1;i++) ifact[i]=mypow(fact[i], MOD-2);
for(int i=0;i<=K;i++)
{
ll res=fact[N+1];
res*=ifact[i]; res%=MOD;
res*=ifact[N+1-i]; res%=MOD;
res*=mypow(K+1-i, N); res%=MOD;
if(i%2==0) ans=(ans+res)%MOD;
else ans=(ans+MOD-res)%MOD;
}
cout << ans;
}
