#include <bits/stdc++.h>

#define VARNAME(x) #x
#define show(x) cerr << #x << " = " << x << endl

using namespace std;
using ll = long long;
using ld = long double;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz:" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = (ll)1e9 + 7LL;
constexpr ld PI = static_cast<ld>(3.1415926535898);

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 10;


int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, K;
    cin >> N >> K;
    vector<ll> a(N);
    for (int i = 0; i < N; i++) {
        cin >> a[i];
    }
    const int SIZE = N * (N - 1) / 2;
    vector<vector<ll>> dp(N + 1, vector<ll>(SIZE + 1, 0));   // 長さiで転倒数j
    vector<vector<ll>> sum(N + 1, vector<ll>(SIZE + 1, 0));  // dp[i][0]+dp[i][1]+...+dp[i][j];
    dp[1][0] = 1;
    sum[1][0] = 1;
    for (int j = 1; j <= SIZE; j++) {
        sum[1][j] += sum[1][j - 1];
    }
    for (int i = 2; i <= N; i++) {
        const int size = i * (i - 1) / 2;
        for (int j = 0; j <= size; j++) {
            const int lower = max(0, j - i + 1);
            const int upper = j;
            const int sumation = (sum[i - 1][upper] - (lower == 0 ? 0LL : sum[i - 1][lower - 1]) + MOD) % MOD;
            dp[i][j] = sumation;
        }
        for (int j = 0; j <= SIZE; j++) {
            sum[i][j] += ((j == 0 ? 0 : sum[i][j - 1]) + dp[i][j]) % MOD;
        }
    }

    cout << sum[N][K] << endl;
    return 0;
}