#include <iostream>
#include <bits/stdc++.h>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
 
int v1[10005];
int nrgen , energy;
int nrg , cgen;
int cf=10005;
int main()
{
 
    f >> nrgen >> energy;
    for (int i=1;i<=energy;i++) {
        v1[i]=2087654321;
    }
    for (int i=1;i<=nrgen;i++) {
        f >> nrg >> cgen;
        for (int j=energy;j>=1;j--) {
            if (j<nrg) {
                v1[j]=min(v1[j],cgen);
            }
            else {
                v1[j]=min(v1[j], v1[j-nrg]+cgen);
            }
        }
    }
    if (v1[energy]==2087654321) {
        g << -1;
    }
    else {
        g << v1[energy];
    }
    return 0;
}