#include <fstream>

using namespace std;
const int nmax = 3e5;
const int extra = 5005;
int dp[nmax];

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

int main()
{
    int n, x, i, j, e, c, ans = 1e9;
    cin >> n >> x;
    for(i = 1; i <= x + extra; i++)
        dp[i] = 1e9;
    for(i = 1; i <= n; i++)
    {
        cin >> e >> c;
        for(j = x + extra; j >= e; j--)
        {
            dp[j] = min(dp[j], dp[j - e] + c);
        }
    }
    for(i = x; i <= x + extra; i++)
        ans = min(ans, dp[i]);
    ans < 1e9 ? cout << ans : cout << -1;
    return 0;
}