#include <bits/stdc++.h>
#define ll long long int
#define pb push_back
#define mp make_pair
#define mod 1000000007
#define pi 3.141592653589793
using namespace std;


int main() {
//    cout << setprecision(10);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    ll n, m;
    cin >> n >> m;
    pair<ll, ll> a[n];
    for (int i = 0; i < n; i++) {
        cin >> a[i].second >> a[i].first;
    }

    ll ans = 0;
    sort(a, a + n, greater<pair<ll, ll>>());
    int d = 0;

    for (auto e : a) {
        if (d + e.second <= m) {
            d++;
            ans += e.first;
        }

    }


    cout << ans;






}