#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
const int INF = 1e9;
int cost[100000];
int main() {
	int n, e;
	in >> n >> e;
	for (int j = 1; j <= e; j++) {
		cost[j] = INF;
	}
	for (int i = 0; i < n; i++) {
		int e_i, c_i;
		in >> e_i >> c_i;
		for (int j = e - 1; j >= 0; j--) {
			if (cost[j] != INF) {
				if (j + e_i >= e) {
					cost[e] = min(cost[e], cost[j] + c_i);
				}
				else {
					cost[j + e_i] = min(cost[j + e_i], cost[j + c_i]);
 				}
			}
		}
	}
	if (cost[e] != INF)out << cost[e];
	else out << -1;
	return 0;
}