#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("rucsac.in");
ofstream g("rucsac.out");
struct hot
{
    int x,y;
};
int cmp(hot a, hot b)
{
    if(a.x!=b.x)
        return a.y<b.y;
    return a.x<b.x;
}
int main()
{
    int n,i,m,p,s=0;
    hot a[100];
    f>>n>>m;
    for(i=1;i<=n;i++)
        f>>a[i].x>>a[i].y;
    sort(a+1,a+n+1,cmp);
    for(i=1;i<=n&&p<=m;i++)
    {
        s=s+a[i].y;
        p=p+a[i].x;
    }
    g<<s;
    return 0;
}