#include <fstream>
#include <algorithm>
using namespace std;
ifstream f ("rucsac.in");
ofstream ge ("rucsac.out");

int n, G,s;

struct rucsac{
    int g, c;
}v[100000];

bool cmp(rucsac a, rucsac b)
{
    if(a.c > b.c){
        return true;
    }
    return false;
}

void afisare()
{
    int i = 0;
    while(G>0){
        if(v[i].g <= G){
            G=G-v[i].g;
            s=s+v[i].c;
        }
        i++;
    }
}

int main()
{
    f>>n>>G;
    for(int i = 0; i < n; i++)
        f>>v[i].g>>v[i].c;
    sort(v, v + n, cmp);
    afisare();
    ge<<s<<"\n";
    return 0;
}