#include <bits/stdc++.h>

using namespace std;

const int inf = 1e9;

int g, w;
struct generator
{
    int energy, cost;
};
vector <int> dp;
vector <generator> generators;

int main()
{
    ios_base :: sync_with_stdio(0);
    cin.tie(0);

    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);

    cin >> g >> w;

    generators.resize(g + 1);
    dp.resize(2 * w + 1, inf);

    int sum = 0;
    for(int i = 1; i <= g; i ++)
    {
        cin >> generators[i].energy >> generators[i].cost;
        sum += generators[i].energy;
    }

    if(sum < w)
    {
        cout << -1;
        return 0;
    }

    dp[0] = 0;
    dp[generators[1].energy] = generators[1].cost;

    for(int i = 2; i <= g; i ++)
    {
        for(int j = 2 * w; j >= 0; j --)
        {
            if(dp[j] != inf  &&  j + generators[i].energy <= 2 * w )
                dp[j + generators[i].energy] = min(dp[j] + generators[i].cost, dp[j + generators[i].energy]);
        }
    }

    int mn = inf;
    for(int i = w; i <= 2 * w; i ++)
        mn = min(mn, dp[i]);
    cout << mn;
    return 0;
}