#include <bits/stdc++.h>

#ifndef Local
#define debug(...) 1337
#define endl '\n'
#endif

using namespace std;

#define int long long

typedef long long ll;
typedef long double ld;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

template<class A, class B>
bool smin(A &x, B &&y) {
        if (x > y) {
                x = y;
                return true;
        }
        return false;
}

template<class A, class B>
bool smax(A &x, B &&y) {
        if (x < y) {
                x = y;
                return true;
        }
        return false;
}

const int inf = 1e18;

struct segTree {
        static const int maxn = 512 * 1024;
        int t[2 * maxn - 1]{};

        void upd(int i, int c) {
                i += maxn - 1;
                t[i] = c;
                while (i) {
                        i = (i - 1) / 2;
                        t[i] = min(t[2 * i + 1], t[2 * i + 2]);
                }
        }

        int lq, rq;

        int get(int i, int l, int r) {
                if (lq <= l && r <= rq)
                        return t[i];
                int m = (l + r) / 2;
                int x = inf;
                if (lq < m)
                        x = get(2 * i + 1, l, m);
                if (m < rq)
                        smin(x, get(2 * i + 2, m, r));
                return x;
        }

        int get(int l, int r) {
                lq = l, rq = r;
                return get(0, 0, maxn);
        }
};

void solve() {
        int n, m;
        cin >> m >> n;
        vector<vector<pair<int, int>>> s(n + 2), t(n + 2);
        for (int i = 0, l, r, c; i < m; ++i) {
                cin >> l >> r >> c;
                s[r].emplace_back(l, c);
                t[l].emplace_back(r, c);
        }

        vector<int> dp(n + 2, inf), pd(n + 2, inf);
        segTree st, ts;
        st.upd(0, 0);
        ts.upd(n + 1, 0);
        dp[0] = 0, pd[n + 1] = 0;

        for (int i = 1; i <= n; ++i) {
                for (auto &[j, c]: s[i])
                        smin(dp[i], st.get(j - 1, i) + c);
                st.upd(i, dp[i]);
        }

        for (int i = n; i >= 1; --i){
                for (auto& [j, c] : t[i])
                        smin(pd[i], ts.get(i + 1, j + 2) + c);
                ts.upd(i, pd[i]);
        }

        debug(dp);
        debug(pd);

        int ans = inf;
        for (int i = 1; i <= n; ++i)
                smin(ans, dp[i - 1] + pd[i + 1]);
        if (ans == inf)
                ans = -1;
        cout << ans << endl;
}

signed main() {
        ios::sync_with_stdio(false), cin.tie(nullptr);

        int tt = 1;
//        cin >> tt;
        while (tt--)
                solve();

        return 0;
}