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



    for (i=1;i<=n;++i)
    {f>>x>>y;
        for ( j=co-x;j>=0;--j)
            b[j+x]=min(b[j+x],b[j]+y);
        for ( j=x;j>=0;--j)
            b[j]=min(b[j],y);
    }
    if (b[co]==999999999)
       g<<"-1"<<'\n';
    else
    g<<b[co]<<'\n';

    return 0;

}