#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

ifstream cin("rucsac.in");
ofstream cout("rucsac.out");

int n,i,a,b,g;
vector <pair<int,int> > el;

int hasonlitka(pair <int,int> a,pair <int,int> b)
{
    if(a.second<b.second) return 0;
    else return 1;
}

int main()
{
    cin>>n>>g;
    for(i=1;i<=n;++i)
    {
        cin>>a>>b;
        el.push_back({a,b});
    }

    sort(el.begin(),el.end(),hasonlitka);

    int suly=0,profit=0;
    i=0;
    while(suly<g && i<n)
    {
        suly+=el[i].first;
        profit+=el[i].second;

        i++;
    }

    cout<<profit;
    return 0;
}