#pragma GCC optimize(3, "unroll-loops", "no-stack-protector")
#define atsum(l, r) accumulate(l, r, 0)
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/hash_policy.hpp>
using namespace std;
using ll = long long;
using ull = unsigned long long;
constexpr int inf = 0x3f3f3f3f;
constexpr ll INF = 0x3f3f3f3f3f3f3f3f;
template <typename T>
inline void chkmin(T &x, T y) { x = min(x, y); }
template <typename T>
inline void chkmax(T &x, T y) { x = max(x, y); }
namespace FastIO
{
// ------------------------------
#define IN_HAS_NEG
#define OUT_HAS_NEG
#define CHK_EOF
#define DISABLE_MMAP
// ------------------------------
#if __cplusplus < 201400
#error Please use C++14 or higher.
#endif
#if __cplusplus > 201700
#define INLINE_V inline
#else
#define INLINE_V
#endif
#if ( defined(LOCAL) || defined (_WIN32) ) && !defined(DISABLE_MMAP)
#define DISABLE_MMAP
#endif
#ifndef DISABLE_MMAP
#include<sys/mman.h>
#endif
#ifdef LOCAL
    inline char gc() { return getchar(); }
    inline void pc(char c) { putchar(c); }
#else
#ifdef DISABLE_MMAP
    INLINE_V constexpr int _READ_SIZE = 1 << 18;
    INLINE_V static char _read_buffer[_READ_SIZE], *_read_ptr = nullptr, *_read_ptr_end = nullptr;
    inline char gc()
    {
        if ( __builtin_expect(_read_ptr == _read_ptr_end, false) )
        {
            _read_ptr = _read_buffer;
            _read_ptr_end = _read_buffer + fread(_read_buffer, 1, _READ_SIZE, stdin);
#ifdef CHK_EOF
            if ( __builtin_expect(_read_ptr == _read_ptr_end, false) ) return EOF;
#endif
        }
        return *_read_ptr++;
    }
#else
    INLINE_V static const char *_read_ptr = (const char *)mmap(nullptr, INT_MAX, 1, 2, 0, 0);
    inline char gc() { return *_read_ptr++; }
#endif
    INLINE_V constexpr int _WRITE_SIZE = 1 << 18;
    INLINE_V static char _write_buffer[_WRITE_SIZE], *_write_ptr = _write_buffer;
    inline void pc(char c)
    {
        *_write_ptr++ = c;
        if ( __builtin_expect(_write_buffer + _WRITE_SIZE == _write_ptr, false) )
        {
            fwrite(_write_buffer, 1, _write_ptr - _write_buffer, stdout);
            _write_ptr = _write_buffer;
        }
    }
    INLINE_V struct _auto_flush
    {
        ~_auto_flush() { fwrite(_write_buffer, 1, _write_ptr - _write_buffer, stdout); }
    }	_auto_flush;
#endif
#ifdef CHK_EOF
    inline bool _isdigit(char c) { return ( c & 16 ) && c != EOF; }
    inline bool _isgraph(char c) { return c > 32 && c != EOF; }
#else
    inline bool _isdigit(char c) { return c & 16; }
    inline bool _isgraph(char c) { return c > 32; }
#endif
    template < class T >
    INLINE_V constexpr bool _is_integer = numeric_limits < T >::is_integer;
    template < class T >
    INLINE_V constexpr bool _is_signed = numeric_limits < T >::is_signed;
    template < class T >
    INLINE_V constexpr bool _is_unsigned = _is_integer < T > && !_is_signed < T >;
    template <> INLINE_V constexpr bool _is_integer < __int128 > = true;
    template <> INLINE_V constexpr bool _is_integer < __uint128_t > = true;
    template <> INLINE_V constexpr bool _is_signed < __int128 > = true;
    template <> INLINE_V constexpr bool _is_unsigned < __uint128_t > = true;
#undef INLINE_V
    inline void read(char &c) { do c = gc(); while ( !_isgraph(c) ); }
    inline void read_cstr(char *s)
    {
        char c = gc(); while ( !_isgraph(c) ) c = gc();
        while ( _isgraph(c) ) *s++ = c, c = gc();
        *s = 0;
    }
    inline void read(string &s)
    {
        char c = gc(); s.clear(); while ( !_isgraph(c) ) c = gc();
        while ( _isgraph(c) ) s.push_back(c), c = gc();
    }
#ifdef IN_HAS_NEG
    template < class T, enable_if_t < _is_signed < T >, int > = 0 >
    inline void read(T &x)
    {
        char c = gc(); bool f = true; x = 0;
        while ( !_isdigit(c) ) { if ( c == 45 ) f = false; c = gc(); }
        if ( f ) while ( _isdigit(c) ) x = x * 10 + ( c & 15 ), c = gc();
        else     while ( _isdigit(c) ) x = x * 10 - ( c & 15 ), c = gc();
    }
    template < class T, enable_if_t < _is_unsigned < T >, int > = 0 >
#else
    template < class T, enable_if_t < _is_integer < T >, int > = 0 >
#endif
    inline void read(T &x)
    {
        char c = gc(); while ( !_isdigit(c) ) c = gc();
        x = 0; while ( _isdigit(c) ) x = x * 10 + ( c & 15 ), c = gc();
    }
    inline void write(char c) { pc(c); }
    inline void write_cstr(const char *s) { while ( *s ) pc(*s++); }
    inline void write(const string &s) { for ( char c : s ) pc(c); }
#ifdef OUT_HAS_NEG
    template < class T, enable_if_t < _is_signed < T >, int > = 0 >
    inline void write(T x)
    {
        char buffer[numeric_limits < T >::digits10 + 1]; int digits = 0;
        if ( x >= 0 )  do buffer[digits++] =  ( x % 10 ) | 48, x /= 10; while ( x );
        else { pc(45); do buffer[digits++] = -( x % 10 ) | 48, x /= 10; while ( x ); }
        while ( digits ) pc(buffer[--digits]);
    }
    template < class T, enable_if_t < _is_unsigned < T >, int > = 0 >
#else
    template < class T, enable_if_t < _is_integer < T >, int > = 0 >
#endif
    inline void write(T x)
    {
        char buffer[numeric_limits < T >::digits10 + 1]; int digits = 0;
        do buffer[digits++] = ( x % 10 ) | 48, x /= 10; while ( x );
        while ( digits ) pc(buffer[--digits]);
    }
    template < int N > struct _tuple_io_helper
    {
        template < class ...T >
        static inline void _read(tuple < T... > &x)
        { _tuple_io_helper < N - 1 >::_read(x), read(get < N - 1 > (x)); }
        template < class ...T >
        static inline void _write(const tuple < T... > &x)
        { _tuple_io_helper < N - 1 >::_write(x), pc(32), write(get < N - 1 > (x)); }
    };
    template <> struct _tuple_io_helper < 1 >
    {
        template < class ...T >
        static inline void _read(tuple < T... > &x) { read(get < 0 > (x)); }
        template < class ...T >
        static inline void _write(const tuple < T... > &x) { write(get < 0 > (x)); }
    };
    template < class ...T >
    inline void read(tuple < T... > &x) { _tuple_io_helper < sizeof...(T) >::_read(x); }
    template < class ...T >
    inline void write(const tuple < T... > &x) { _tuple_io_helper < sizeof...(T) >::_write(x); }
    template < class T1, class T2 >
    inline void read(pair < T1, T2 > &x) { read(x.first), read(x.second); }
    template < class T1, class T2 >
    inline void write(const pair < T1, T2 > &x) { write(x.first), pc(32), write(x.second); }
    template < class T1, class ...T2 >
    inline void read(T1 &x, T2 &...y) { read(x), read(y...); }
    template < class ...T >
    inline void read_cstr(char *x, T *...y) { read_cstr(x), read_cstr(y...); }
    template < class T1, class ...T2 >
    inline void write(const T1 &x, const T2 &...y) { write(x), write(y...); }
    template < class ...T >
    inline void write_cstr(const char *x, const T *...y) { write_cstr(x), write_cstr(y...); }
    template < class T >
    inline void print(const T &x) { write(x); }
    inline void print_cstr(const char *x) { write_cstr(x); }
    template < class T1, class ...T2 >
    inline void print(const T1 &x, const T2 &...y) { print(x), pc(32), print(y...); }
    template < class ...T >
    inline void print_cstr(const char *x, const T *...y) { print_cstr(x), pc(32), print_cstr(y...); }
    inline void println() { pc(10); }
    inline void println_cstr() { pc(10); }
    template < class ...T >
    inline void println(const T &...x) { print(x...), pc(10); }
    template < class ...T >
    inline void println_cstr(const T *...x) { print_cstr(x...), pc(10); }
}
using namespace FastIO;
template <typename T>
inline void clear(T &x) {
    T y;
    swap(x, y);
}
template <uint32_t mod = 1000000007>
class Modint {
   private:
    static constexpr uint32_t get_r() {
        uint32_t ret = mod;
        for (int i = 0; i < 4; i++) ret *= 2 - mod * ret;
        return ret;
    }
    static constexpr uint32_t r = get_r();
    static constexpr uint32_t n2 = -uint64_t(mod) % mod;
    static_assert(r * mod == 1 && mod < (1 << 30) && mod & 1);
    uint32_t data;

   public:
    constexpr Modint() : data(0) {}
    template <class int_t>
    constexpr Modint(const int_t x)
        : data(reduce(
              uint64_t((sizeof(int_t) < sizeof(uint32_t) ? x : x % int_t(mod)) +
                       mod) *
              n2)){};
    static constexpr uint32_t reduce(const uint64_t x) {
        return (x + uint64_t(uint32_t(x) * (-r)) * mod) >> 32;
    }
    constexpr Modint &operator+=(const Modint &r) {
        if (int32_t(data += r.data - 2 * mod) < 0) {
            data += 2 * mod;
        }
        return *this;
    }
    constexpr Modint &operator-=(const Modint &r) {
        if (int32_t(data -= r.data) < 0) {
            data += 2 * mod;
        }
        return *this;
    }
    constexpr Modint &operator*=(const Modint &r) {
        return data = reduce((uint64_t)data * r.data), *this;
    }
    constexpr Modint &operator/=(const Modint &r) { return *this *= r.inv(); }
    constexpr friend Modint operator+(Modint l, const Modint &r) {
        return l += r;
    }
    constexpr friend Modint operator-(Modint l, const Modint &r) {
        return l -= r;
    }
    constexpr friend Modint operator*(Modint l, const Modint &r) {
        return l *= r;
    }
    constexpr friend Modint operator/(Modint l, const Modint &r) {
        return l /= r;
    }
    constexpr friend bool operator==(Modint l, const Modint &r) {
        return l.value() == r.value();
    }
    constexpr Modint operator-() const { return Modint() - Modint(*this); }
    template <class int_t>
    constexpr Modint pow(int_t r) const {
        Modint res(1), w(*this);
        for (; r; r >>= 1, w *= w)
            if (r & 1) res *= w;
        return res;
    }
    constexpr Modint inv() const { return pow(mod - 2); }
    constexpr uint32_t value() const {
        uint32_t res = reduce(data);
        return res >= mod ? res - mod : res;
    }
};
using modint = Modint<>;
const int N = 155;
int n, X, pu, p[N];
modint inv[N * N], ans;
void dfs(int u, basic_string<int> cur) {
    if (u == n + 1) {
        memset(p, 0, sizeof(p));
        
        for (int v : cur) ++p[v];
        for (int i = 1; i <= n; i++) p[i] += p[i - 1];
        int cc = 0;
        for (int l = 1; l <= n; l++)
            for (int r = l; r <= n; r++)
                if (l <= X && X <= r) {
                    if (p[l - 1] || p[n] != p[r]) ++cc;
                } else {
                    if (p[l - 1] != p[r]) ++cc;
                }
        // for (int v : cur) cerr << v << endl;
        if (cur.size() & 1)
            ans += modint(n * (n + 1) / 2) * inv[cc];
        else 
            ans -= modint(n * (n + 1) / 2) * inv[cc];
        return;
    }
    if (u == X || u == pu) return dfs(u + 1, cur);
    dfs(u + 1, cur);
    dfs(u + 1, cur + u);
}
inline void solve(int u) {
    pu = u;
    dfs(1, {});
}
int main() {
    read(n, X);
    assert(n <= 20);
    for (int i = 1; i <= n * n; i++) inv[i] = modint(i).inv();
    for (int i = 1; i <= n; i++)
        if (i != X) solve(i);
    println((ans * inv[n - 1]).value());
    return 0;
}
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