#include <fstream>
#include <iostream>
using namespace std;

#define inf 1000

ifstream fi("energii.in");
ofstream fo("energii.out");

int a[100000],i,j,c,p,g,w;

int main(){
	
	fi >> g >> w;
	for (i=1; i<=w+10001; i++) a[i]=inf;

	for (i=1; i<=g; i++){
		fi >> p >> c;
		for (j=w; j>=0; j--)
			if (a[j]+c<a[j+p]) a[j+p]=a[j]+c;
	}

	c=inf;
	for (i=w; i<=w+10001; i++) if (a[i]<c) c=a[i];
	
	if (c==inf) fo << "-1"; else fo << c;
	
	return 0;
}