// includes #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include // macros #define ll long long int #define pb emplace_back #define mk make_pair #define pq priority_queue #define FOR(i, a, b) for(int i=(a);i<(b);++i) #define rep(i, n) FOR(i, 0, n) #define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--) #define all(x) (x).begin(),(x).end() #define sz(x) ((int)(x).size()) #define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end()) using namespace std; // types typedef pair P; typedef pair Pl; typedef pair Pll; typedef pair Pd; // constants const int inf = 1e9; const ll linf = 1LL << 50; const double EPS = 1e-10; const int mod = 1e9 + 7; // solve template bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;} template bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;} int main(int argc, char const* argv[]) { ios_base::sync_with_stdio(false); cin.tie(0); int n; ll k; cin >> n >> k; vector a(n); rep(i, n)cin >> a[i]; sort(all(a)); vector lv, rv; for(int i = 0; i < n; i++){ if(a[i] <= k / 2)lv.pb(a[i]); else rv.pb(a[i]); } ll res = 1; if(sz(rv) > sz(lv)){ cout << 0 << endl; return 0; } reverse(all(rv)); for(int i = 0; i < sz(rv); i++){ int index = upper_bound(all(lv), k - rv[i]) - lv.begin(); index--; if(index < 0)res = 0; else{ res = res * (index + 1 - i) % mod; } } int m = sz(lv) - sz(rv); for(int i = m - 1; i > 0; i-=2){ res = res * i % mod; } cout << res << endl; return 0; }