///dp[i]-costul minim pt energia i?

#include <fstream>
#define int long long

using namespace std;

ifstream cin ("energii.in");
ofstream cout ("energii.out");

const int MAX = 10000;
const int INF = 1e9;
const int N = 5000;
int dp[MAX + 1];

struct clasa
{
    int e, cost;
} a[N + 1];

int n, energ, mx;

signed main()
{
    cin >> n >> energ;
    for (int i = 1; i <= n; ++i)
        cin >> a[i].e >> a[i].cost, mx += a[i].e;
    mx = min (mx, MAX);
    for (int i = 1; i <= mx; ++i)
        dp[i] = INF;
    for (int i = 1; i <= n; ++i)
    {
        for (int j = mx - a[i].e; j >= 0; --j)
            if (dp[j] != INF)
                dp[j + a[i].e] = min (dp[j + a[i].e], dp[j] + a[i].cost);
    }
    int mn = INF;
    for (int i = energ; i <= mx; ++i)
        mn = min (mn, dp[i]);
    if (mn == INF)
        cout << "-1\n";
    else
        cout << mn << "\n";
    return 0;
}