#include <bits/stdc++.h>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
int e[1005],c[1005];
vector<int> d;
int main() {
	int n,s;
	in>>n>>s;
	for(int i=1;i<=n;i++)in>>e[i]>>c[i];
	d=vector<int>(s+1,1000005);
	d[0]=0;
	for(int i=1;i<=n;i++)
	for(int j=s;j>=0;j--)
	if(j<=e[i])d[j]=min(d[j],c[i]);
	else d[j]=min(d[j],d[j-e[i]]+c[i]);
	out<<(d[s]==1000005 ? -1 : d[s]);
	return 0;
}