#include using namespace std; using VS = vector; using LL = long long; using VI = vector; using VVI = vector; using PII = pair; using PLL = pair; using VL = vector; using VVL = vector; #define ALL(a) begin((a)),end((a)) #define RALL(a) (a).rbegin(), (a).rend() #define SZ(a) int((a).size()) #define SORT(c) sort(ALL((c))) #define RSORT(c) sort(RALL((c))) #define UNIQ(c) (c).erase(unique(ALL((c))), end((c))) #define FOR(i, s, e) for (int(i) = (s); (i) < (e); (i)++) #define FORR(i, s, e) for (int(i) = (s); (i) > (e); (i)--) #define debug(x) cerr << #x << ": " << x << endl const int INF = 1e9; const LL LINF = 1e16; const LL MOD = 1000000007; const double PI = acos(-1.0); int DX[8] = { 0, 0, 1, -1, 1, 1, -1, -1 }; int DY[8] = { 1, -1, 0, 0, 1, -1, 1, -1 }; /* ----- 2018/09/23 Problem: yukicoder 271 / Link: http://yukicoder.me/problems/no/271 ----- */ /* ------問題------ -----問題ここまで----- */ /* -----解説等----- ----解説ここまで---- */ template struct BIT { // 1-index int N; int nn; vector data; BIT(int n) { N = n + 1; data = vector(n + 1, 0); nn = 1; while (nn * 2 <= N)nn *= 2; } void add(int i, type w) { // a[i] += w for (int x = i; x <= N; x += x & -x) { data[x] += w; } } type sum(int i) { // iまでの和 [1,i] type ret = 0; for (int x = i; x > 0; x -= x & -x) { ret += data[x]; } return ret; } // [l, r] type sum(int l, int r) { if (l > r) return 0; return sum(r) - sum(l - 1); } }; template <::std::uint_fast32_t MODULO> class modint { public: using uint32 = ::std::uint_fast32_t; using uint64 = ::std::uint_fast64_t; using value_type = uint32; uint32 a; modint() noexcept : a(0) {}modint(const uint32 x) noexcept : a(x) {}modint operator+(const modint &o) const noexcept { return a + o.a < MODULO ? modint(a + o.a) : modint(a + o.a - MODULO); }modint operator-(const modint &o) const noexcept { return modint(a < o.a ? a + MODULO - o.a : a - o.a); }modint operator*(const modint &o) const noexcept { return modint(static_cast(a) * o.a % MODULO); }modint operator/(const modint &o) const { return modint(static_cast(a) * (~o).a % MODULO); }modint &operator+=(const modint &o) noexcept { return *this = *this + o; }modint &operator-=(const modint &o) noexcept { return *this = *this - o; }modint &operator*=(const modint &o) noexcept { return *this = *this * o; }modint &operator/=(const modint &o) { return *this = *this / o; }modint operator~() const noexcept { return pow(MODULO - 2); }modint operator-() const noexcept { return a ? modint(MODULO - a) : *this; }modint operator++() noexcept { return a == MODULO - 1 ? a = 0 : ++a, *this; }modint operator--() noexcept { return a ? --a : a = MODULO - 1, *this; }bool operator==(const modint &o) const noexcept { return a == o.a; }bool operator!=(const modint &o) const noexcept { return a != o.a; }bool operator<(const modint &o) const noexcept { return a < o.a; }bool operator<=(const modint &o) const noexcept { return a <= o.a; }bool operator>(const modint &o) const noexcept { return a > o.a; }bool operator>=(const modint &o) const noexcept { return a >= o.a; }explicit operator bool() const noexcept { return a; }explicit operator uint32() const noexcept { return a; }modint pow(uint32 x) const noexcept { uint64 t = a, u = 1; while (x) { if (x & 1)u = u * t % MODULO; t = (t * t) % MODULO; x >>= 1; } return modint(u); } uint32 get() const noexcept { return a; } }; using mint = modint; struct factorialNums { VL a; vector fact; factorialNums(VL &p):a(SZ(p)),fact(1e5+5) { BITbit(SZ(p)); FORR(i, SZ(p) - 1, 0 - 1) { a[i] = bit.sum(p[i]); bit.add(p[i], 1); } fact[0] = 1; FOR(i, 1, SZ(fact)) { fact[i] = mint(i) * fact[i - 1]; } } mint add(LL K) { FOR(i, 0, SZ(a)) { LL t = K + a[SZ(a) - 1 - i]; a[SZ(a) - 1 - i] = t % (i + 1); K = t / (i + 1); } return mint(K); } mint inv() { mint ret = 0; mint v = 0; mint f = 1; FORR(i, SZ(a) - 1, 0 - 1) { mint k = SZ(a) - 1 - i; ret += mint(a[i]) * fact[k.get()] * k*(k - 1) / mint(4); ret += f * mint(a[i])*mint(a[i] - 1) / mint(2); ret += mint(a[i])*v; v += mint(a[i])*f; f *= SZ(a) - i; } return ret; } }; int main() { cin.tie(0); ios_base::sync_with_stdio(false); LL N, K; cin >> N >> K; VL p(N); FOR(i, 0, N) { cin >> p[i]; } factorialNums fns(p); mint i1 = fns.inv(); mint m = fns.add(K); mint i2 = fns.inv(); mint ans = 0; ans = m * fns.fact[N] * N*(N - 1)/(mint(4)) + i2 - i1; cout << ans.get() << "\n"; return 0; }