#include <fstream>
#define minim(a,b) (a<b)?a:b
using namespace std;

ifstream f("energii.in");
ofstream output("energii.out");
int g,energmax,i,j;
int energ,cost;
int a[100000]; // a[energie] = cost

int main() {
    f >> g >> energmax;
    for (i=1;i<=g;i++) {
        f >> energ >> cost;
        for (j=2*energmax; j>= 1 ; j--) {
            if (a[j]!= 0) {
                a[j+energ] = minim(a[j+energ],a[j]+cost);
            }
        }
        if (a[energ] != 0) a[energ] = min(a[energ],cost);
        else a[energ] = cost;
    }
    cost = 2000000000;
    for (i=energmax;i<=90000;i++) {
        if (a[i]!= 0) cost = minim(cost,a[i]);
    }
    if (cost > 0) output << cost;
    else output << -1;
    return 0;
}