#include <bits/stdc++.h>
#define range(i, l, r) for(int (i) = (l); (i) < (r); (i)++)
#define reversed_range(i, l, r) for (int (i) = (r) - 1; (i) >= l; (i)--)
using namespace std;
template <typename T>
using vec = vector<T>;
using lint = long long;
using ulint = unsigned long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;

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

template <typename T>
ostream& operator <<(ostream& os, vec<T> v) {
    os << "[";
    if (v.size() == 0) return os << "]";
    for (int i = 0; i < v.size() - 1; i++) {
        os << v.at(i) << ", ";
    }
    return os << v.at(v.size() - 1) << "]";
}

template <typename T>
ostream& operator <<(ostream& os, set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    cout << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        cout << ", " << *it;
    }
    return cout << "}";
}

template <typename T>
ostream& operator <<(ostream& os, unordered_set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    cout << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        cout << ", " << *it;
    }
    return cout << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    cout << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        cout << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, unordered_map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    cout << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        cout << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

lint pow(lint num, lint e, lint MOD) {
    lint res = 1;
    lint cur_num = num;
    while (e) {
        if (e & 1) {
            res *= cur_num;
            res %= MOD;
        }
        cur_num *= cur_num;
        cur_num %= MOD;
        e >>= 1;
    }
    return res;
}

int main_old() {
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    lint N, M;
    cin >> N >> M;
    vec<plint> jobs(N);
    range(i, 0, N) {
        lint A, B;
        cin >> A >> B;
        if (A <= M) {
            jobs.at(i) = {B, A};
        }
    }
    sort(jobs.begin(), jobs.end(), greater<plint>());
    set<lint> available_slots;
    range(i, 1, M + 1) available_slots.emplace(i);
    lint max_total_profit = 0;
    for (const auto job : jobs) {
        lint days, profit;
        tie(profit, days) = job;
        auto it = available_slots.lower_bound(days);
        if (it != available_slots.end()) {
            max_total_profit += profit;
            available_slots.erase(it);
        }
    }
    cout << max_total_profit << "\n";
}

int main() {
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    lint N, M;
    cin >> N >> M;
    vec<plint> jobs(N);
    range(i, 0, N) {
        lint days, profit;
        cin >> days >> profit;
        jobs.at(i) = {profit, days};
    }
    sort(jobs.begin(), jobs.end(),
        [](const plint& a, const plint& b) {
            return a.second < b.second;
        });
    priority_queue<plint> available_jobs;
    lint cur_idx = 0, max_profit = 0;
    range(d, 1, M + 1) {
        while (cur_idx < N and jobs.at(cur_idx).second <= d) {
            available_jobs.push(jobs.at(cur_idx));
            cur_idx += 1;
        }
        if (!available_jobs.empty()) {
            max_profit += available_jobs.top().first;
            available_jobs.pop();
        }
    }
    cout << max_profit << "\n";
}

Measured memory_bytes: 3956