#include <fstream>

using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int INF=(1<<30),G,w,d[1002][5002],o,l,e[1002],c[1002],i,n,j;
int main()
{
     f>>n>>G;
     for (i=1;i<=n;i++)
     f>>e[i]>>c[i];
     for (i=0;i<=n;i++)
         for (j=1;j<=G;j++)
         d[i][j]=INF;
     for (i=1;i<=n;i++)
     {
       for(j=1;j<=G;j++)
       if (e[i]<=j) d[i][j]=min(d[i-1][j],d[i-1][j-o]+c[i]);
       else d[i][j]=min(d[i-1][j],c[i]);
     }
    if (d[n][G]==INF) g<<-1<<'\n';
    else g<<d[n][G]<<'\n';
    return 0;
}