#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <memory.h>

using namespace std;

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

const int Gmax = 1010;
const int Wmax = 15005;
const int oo = 0x3f3f3f3f;

int G, W, E, C, DP[Wmax];

int main()
{
    fin>>G>>W;
    memset(DP, oo, sizeof DP); DP[0] = 0;

    for(int i=1; i <= G; i++)
    {
        fin>>E>>C;
        for(int j=W; j >= 0; j--)
            DP[j + E] = min(DP[j + E], DP[j] + C);
    }

    int minim = oo;
    for(int i=W; i < Wmax; i++)
        minim = min(minim, DP[i]);
    if(minim != oo)
        fout<<minim;
    else
        fout<<"-1";
    fin.close();
    fout.close();
    return 0;
}