#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;}