#include <fstream>
using namespace std;
  
int e[15000],c[15000],d[15000];
ifstream in("energii.in");
ofstream out("energii.out"); 

int main(){
	int s,i,j,n,g,v[100],e[100],c[100],sol=100000;
	in>>n>>g;
	for (i=1;i<=n;i++){
		in>>e[i]>>c[i];
		s+=e[i];
	}
	if (s<g) out<<"-1";
	else{
		for(i=1;i<=s;i++)
		v[i]=100000;
		v[0]=0;
		for (i=1;i<=n;i++)
		for (j=g-1;j>=0;j--)
		if ((v[j]!=100000)&&(v[j+e[i]]>v[j]+c[i])) v[j+e[i]]=v[j]+c[i];
		for (i=g;i<=s;i++)
		if(v[i]<sol) sol=v[i];
		out<<sol;
		}
}