#include <iostream>
#include <fstream>
using namespace std;

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

const int dmax = 1002;
const int W_max = 10011001;

int e[dmax];
int c[dmax];

int cost[W_max]; //cost[i] == COSTUL MINIM NECESAR PRODUCERII ENERGIEI i

int N, W;

int main()
{
    int i, j, S = 0, Min;

    in >> N; // NR GENERATOARE
    in >> W; //ENERGIE NECESARA REPORNIRII CENTRALEI

    for(i = 1; i <= N; i++)
    {
        in >> e[i] >> c[i];

        S += e[i];
    }

    if(S < W) out << -1;
    else
    {

        for(i = 1; i <= S; i++) cost[i] = -1;

        cost[0] = 0;

        for(i = 1; i <= N; i++)
            for(j = S; j >= e[i]; j--)
                if(cost[j - e[i]] != -1 &&
                        ( cost[j] > cost[j - e[i]] + c[i] || cost[j] == -1)  )

                    cost[j] = cost[j - e[i]] + c[i];

        //for(i = 0; i <= S; i++) cout << cost[i] << " ";

        Min = cost[W];

        for(i = W + 1; i <= S; i++)
            if(cost[i] < Min && cost[i] != -1) Min = cost[i];

        out << Min;

    }

    return 0;
}