import java.util.*; import java.io.*; import java.math.*;
public class Main{
	static void solve(){//Here is the main function
		ArrayList<Integer> one = nextIntArray();
		int N = one.get(0);
		int K = one.get(1);
		int mod = 1000000007;
		Combination comb = new Combination(N, mod);
		long output = 1;
		for(int i = 1; i <= Math.min(N, K); i++){
			long tmp = comb.nCk(N, i, mod);
			tmp %= mod;
			tmp *= comb.nCk(N - 1, i, mod);
			tmp %= mod;
			output += tmp;
			output %= mod;
		}
		myout(output);
	}
	//Method addition frame start

static class Combination{
        long[] kaijo;
        long[] inverse;
        Combination(int N, long mod){
                kaijo = new long[N + 1];
                inverse = new long[N + 1];
                kaijo[0] = 1;
                inverse[0] = 1;
                for(int i = 1; i <= N; i++){
                        kaijo[i] = kaijo[i - 1] * (long)i % mod;
                        inverse[i] = inverse[i - 1] * this.pow((long)i, mod - 2, mod) % mod;
                }
        }
        private long pow(long x, long n, long m) {
	        long ans = 1;
	        while (n > 0) {
	                if ((n & 1) == 1){
	                  ans = ans * x;
	                  if(m != -1){ans %= m;}
	                }
	                x = x * x;
	                if(m != -1){x %= m;}
	                n >>= 1;
	        }
	        return ans;
        }
        public long nCk(int n, int k, long mod){
        	if(k < 0 || k > n){
        		return 0;
        	}
        	return ((kaijo[n] * inverse[k]) % mod * inverse[n - k]) % mod;
        }
}

	//Method addition frame end

	//Don't have to see. start------------------------------------------
	static class InputIterator{
		ArrayList<String> inputLine = new ArrayList<String>(1024);
		int index = 0; int max; String read;
		InputIterator(){
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			try{
				while((read = br.readLine()) != null){
					inputLine.add(read);
				}
			}catch(IOException e){}
			max = inputLine.size();
		}
		boolean hasNext(){return (index < max);}
		String next(){
			if(hasNext()){
				return inputLine.get(index++);
			}else{
				throw new IndexOutOfBoundsException("There is no more input");
			}
		}
	}
	static HashMap<Integer, String> CONVSTR = new HashMap<Integer, String>();
	static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem.
	static PrintWriter out = new PrintWriter(System.out);
	static void flush(){out.flush();}
	static void myout(Object t){out.println(t);}
	static void myerr(Object t){System.err.print("debug:");System.err.println(t);}
	static String next(){return ii.next();}
	static boolean hasNext(){return ii.hasNext();}
	static int nextInt(){return Integer.parseInt(next());}
	static long nextLong(){return Long.parseLong(next());}
	static double nextDouble(){return Double.parseDouble(next());}
	static ArrayList<String> nextStrArray(){return myconv(next(), 8);}
	static ArrayList<String> nextCharArray(){return myconv(next(), 0);}
	static ArrayList<Integer> nextIntArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Integer> ret = new ArrayList<Integer>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Integer.parseInt(input.get(i)));
		}
		return ret;
	}
	static ArrayList<Long> nextLongArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Long> ret = new ArrayList<Long>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Long.parseLong(input.get(i)));
		}
		return ret;
	}
	static String myconv(Object list, int no){//only join
		String joinString = CONVSTR.get(no);
		if(list instanceof String[]){
			return String.join(joinString, (String[])list);
		}else if(list instanceof ArrayList){
			return String.join(joinString, (ArrayList)list);
		}else{
			throw new ClassCastException("Don't join");
		}
	}
	static ArrayList<String> myconv(String str, int no){//only split
		String splitString = CONVSTR.get(no);
		return new ArrayList<String>(Arrays.asList(str.split(splitString)));
	}
	public static void main(String[] args){
		CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, "");
		solve();flush();
	}
	//Don't have to see. end------------------------------------------
}


Measured memory_bytes: 36256