#include <fstream>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
#define inf 999999999
int i,j,x,y,n,w,b[5002];
int main()
{ f>>n>>w;
  for(i=1;i<=w+1;++i)
    b[i]=inf;
    b[0]=0;
  for(i=1;i<=n;++i)
  {f>>x>>y;
        for ( j=w-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[w]==999999999)
       g<<"-1"<<'\n';
    else
    g<<b[w]<<'\n';
    return 0;
}