#include <algorithm>
#include <fstream>
using namespace std;
ifstream fin("ssm.in");
ofstream fout("ssm.out");

pair<int, int> v[5001];

bool compare(pair<int,int> a, pair<int,int> b)
{
    return (a.second > b.second);
}
int main()
{
    int n, g;
    fin >> n >> g;
    for (int i = 1; i <= n; i++)
        fin >> v[i].first >> v[i].second;
    sort(v + 1, v + n + 1, compare);
    int sum=0;
    int ind = 1;
    int val = 0;
    for (int i = 1; i <= n; i++)
    {
        if (sum + v[i].first > g)
            break;
        else
            sum += v[i].first, val += v[i].second;
    }
    fout << val;
    return 0;
}