#include <fstream>
#include <algorithm>
using namespace std;
const int INF = (int) 1e9;
int main() {
	ifstream cin("energii.in");
	ofstream cout("energii.out");
	//dp[G+1][W+1] - costul minim pentru a genera o en. mai mare sau egala cu W folosind o submultime a primelor G elemente 
	int G, W;
	cin >> G >> W;
	int EG[G+1], CG[G+1];
	for(int i=1;i<=G;i++)
		cin >> EG[i] >> CG[i];
	int S=0;
	for(int i=1;i<=G;i++)
		S+=EG[i];
	if(S<W) {
		cout << -1;
		return 0;
	}
	int dp[S+1]; 
	dp[0] = 0;
	for(int i=1;i<=S;i++)
		dp[i] = INF;
	for(int i=1;i<=G;i++) {
		for(int j=S;j>=1;j--) {
			if(j>=EG[i])
				dp[j] = min(dp[j], dp[j-EG[i]]+CG[i]);
		}	
	}
	
	int MN = dp[W];
	for(int i=W+1;i<=S;i++)
		MN=min(MN, dp[i]);
	cout << MN;
	return 0;
	
}