#include <fstream>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int n,co,x,y,s,i,j,mi,b[5010];
int main()
{   f>>n>>co;
    f>>x>>y;
    b[x]=y;
    s=x;
    for (i=2;i<=n;++i) {
        f>>x>>y;
        for (j=s-x;j>=1;--j) {
            if (b[j]>0)
                if (b[j+x]==0 || b[j+x]<b[j]+y)
                    b[j+x]=b[j]+y;}
        if (b[x]==0 || b[x]>y)
            b[x]=y;
        s+=x;
        if (s>co)
            s=co;
        }

    if (b[co]==0)
        g<<-1<<'\n';
    else
        g<<b[co]<<'\n';

    return 0;
}