#include <fstream>
using namespace std;
ifstream fi("energii.in");
ofstream fo("energii.out");
int Inf=2000000,n,g,e,p,i,j,c[5001];
int main()
{fi>>n>>g;
for (i=1;i<=g;i++)c[i]=Inf;
for(i=1;i<=n;i++)
   {fi>>e>>p;
    for( j=g;j>=0;j--)
    if(j<=e) c[j]=min(c[j],p);
        else c[j]=min(c[j],c[j-e]+p);
   }
if (c[g]!=Inf )fo<<c[g]; else fo<<"-1";
    return 0;
}