#include<iostream>
#include<fstream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;

struct coord
{
    int ener,cost;
};

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

int n,Gmax;
coord g[1005],mat1[12005],mat2[12005];
int suma;

inline void Citire()
{
    fin>>n>>Gmax;
    for (int i=1;i<=n;i++)
        {
            fin>>g[i].ener>>g[i].cost;
            if (g[i].ener>Gmax)
                g[i].ener=Gmax;
            suma+=g[i].ener;
        }
}

inline void Rezolva()
{
    int i,j,minim=2000000000    ;
    for (int i=1;i<=12000;i++)
        mat1[i].cost=mat2[i].cost=2000000000;
    for (i=1;i<=n;i++)
        {
            for (j=1;j<=12000;j++)
            {
                mat2[j]=mat1[j];
                if (j>=g[i].ener)
                   mat2[j].cost=min(mat1[j-g[i].ener].cost + g[i].cost,mat1[j].cost);

            }
            for (j=1;j<=12000;j++)
                mat1[j]=mat2[j];
        }
    for (i=Gmax;i<=12000;i++)
        if (mat2[i].cost<minim)
            minim=mat2[i].cost;
    fout<<minim<<"\n";
}

int main()
{
    Citire();
    if (suma<Gmax)
        fout<<"-1\n";
    else
        Rezolva();
    return 0;
}