import java.io.*;
import java.util.Arrays;

/**
 * @author tutuz on 2020/04/05
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskX solver = new TaskX();
        solver.solve(1, in, out);
        out.close();
    }

    static int INF = 1 << 30;
    static long LINF = 1L << 55;
    static int MOD = 1000000007;
    static int[] mh4 = {0, -1, 1, 0};
    static int[] mw4 = {-1, 0, 0, 1};
    static int[] mh8 = {-1, -1, -1, 0, 0, 1, 1, 1};
    static int[] mw8 = {-1, 0, 1, -1, 1, -1, 0, 1};

    static class TaskX {

        public void solve(int testNumber, MyInput in, PrintWriter out) {

            int n = in.nextInt(), k = in.nextInt();

            long ans = 0;
            for (int i = 0; i < n && i <= k; i++) {
                ans += (comb(n, i) % MOD) * h(n - i, i) % MOD;
                ans %= MOD;
            }

            out.println(ans);
        }
    }

    /**
     * 二項係数
     * 前提 n < modP
     * nCr = n!/(r!*(n-r)!)である。この時分子分母にMODが来る場合は以下のように使用する
     */
    public static long h(int n, int r) {
        return comb(n + r - 1, r) % MOD;
    }

    public static long comb(int n, int r) {
        if (r < 0 || r > n) return 0L;
        return fact[n] % MOD * factInv[r] % MOD * factInv[n - r] % MOD;
    }

    public static int MAXN = 300000;

    static long[] fact = factorialArray(MAXN, MOD);
    static long[] factInv = factorialInverseArray(MAXN, MOD, inverseArray(MAXN, MOD));

    public static long[] factorialArray(int maxN, long mod) {
        long[] fact = new long[maxN + 1];
        fact[0] = 1 % mod;
        for (int i = 1; i <= maxN; i++) {
            fact[i] = fact[i - 1] * i % mod;
        }
        return fact;
    }

    public static long[] inverseArray(int maxN, long modP) {
        long[] inv = new long[maxN + 1];
        inv[1] = 1;
        for (int i = 2; i <= maxN; i++) {
            inv[i] = modP - (modP / i) * inv[(int) (modP % i)] % modP;
        }
        return inv;
    }

    public static long[] factorialInverseArray(int maxN, long modP, long[] inverseArray) {
        long[] factInv = new long[maxN + 1];
        factInv[0] = 1;
        for (int i = 1; i <= maxN; i++) {
            factInv[i] = factInv[i - 1] * inverseArray[i] % modP;
        }
        return factInv;
    }

    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];

        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }

        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }

        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }

        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++)
                ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public long nextLong() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            long ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++)
                ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }

        public String nextString() {
            return new String(nextChars());
        }

        public char[] nextChars() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            return Arrays.copyOf(str, len);
        }

        public char[][] next2DChars(int h, int w) {
            char[][] s = new char[h][w];
            for (int i = 0; i < h; i++) {
                s[i] = nextChars();
            }
            return s;
        }

        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (EndOfFileRuntimeException e) {
            }
            return len;
        }

        public int[] nextIntArray(final int n) {
            final int[] res = new int[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextInt();
            }
            return res;
        }

        public int[] nextIntArray1Index(final int n) {
            final int[] res = new int[n + 1];
            for (int i = 1; i < n + 1; i++) {
                res[i] = nextInt();
            }
            return res;
        }

        public int[] nextIntArrayDec(final int n) {
            final int[] res = new int[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextInt() - 1;
            }
            return res;
        }

        public long[] nextLongArray(final int n) {
            final long[] res = new long[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextLong();
            }
            return res;
        }

        public long[] nextLongArray1Index(final int n) {
            final long[] res = new long[n + 1];
            for (int i = 1; i < n + 1; i++) {
                res[i] = nextLong();
            }
            return res;
        }

        public long[] nextLongArrayDec(final int n) {
            final long[] res = new long[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextLong() - 1;
            }
            return res;
        }

        public double nextDouble() {
            return Double.parseDouble(nextString());
        }

        public double[] nextDoubleArray(int n) {
            double[] res = new double[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextDouble();
            }
            return res;
        }

        static class EndOfFileRuntimeException extends RuntimeException {
        }

    }
}


Measured memory_bytes: 29524