#include <iostream>
#include <fstream>
#define gmax 1005
#define wmax 5005
#define inf 9999999
using namespace std;

int dp[gmax][wmax];

int main() {
	ifstream f("energii.in");
	ofstream g("energii.out");

	int G, N, i, j, w[10005], p[10005];

	f>>N>>G;

	for(i=1; i<=N; i++) {
		f>>p[i]>>w[i];
	}

	for(i=0; i<=N; i++)
		for(j=0; j<=G; j++)
			dp[i][j]=inf;
    dp[0][0] = 0;
	for(i=1; i<=N; i++) {
		for(j=0; j<=G; j++) {

			dp[i][j] = min( dp[i-1][j], w[i] );

			if(p[i] <= j) {
				dp[i][j] = min( dp[i-1][j], w[i] + dp[i-1][j-p[i]] );
			}

		}
	}

/*	for(i=0; i<=N; i++) {
		for(j=1; j<=G; j++) {
			g<<dp[i][j]<<" ";
		}
		g<<"\n";
	}
*/
	if(dp[N][G]==inf) dp[N][G] = -1;

	g<<dp[N][G]<<"\n";

	f.close();
	g.close();
	return 0;
}