#include <bits/stdc++.h>
using namespace std;
ifstream in ("energii.in");
ofstream out ("energii.out");
int N, E;
vector <pair <int , int> > v;
int ans[20001];
main()
{
    in >> N >> E;
    for (int i = 1;i<=10000;++i)
        ans[i] = 1<<30;
    for (;N--;)
    {
        int eng, cost;
        in >> eng >> cost;
        for (int j = 10000 - eng;j>=0;--j)
            if (ans[j]!=1<<30)
                ans[j + eng] = min(ans[j + eng], ans[j] + cost);
        ans[eng] = min(ans[eng], cost);
    }
    int anss = 1<<30;
    for (int i = E; i<=10000;++i)
        anss = min (anss, ans[i]);
    if (anss == 1<<30)
        out << -1 << '\n';
    else
        out << anss << '\n';
    return 0;
}