#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;
for (int i=1;i<=co+1;++i)
b[i]=999999999;





    for (i=1;i<=n;++i) {
        f>>x>>y;
        for (j=co-x;j>=1;--j) {

                if ( b[j+x]<b[j]+y)
                    b[j+x]=b[j]+y;}
                     for ( j=x;j>=0;--j)

            if ( b[j]>y)
                b[j]=y;


        }

    if (b[co]==999999999)
        g<<-1<<'\n';
    else
        g<<b[co]<<'\n';

    return 0;
}