#include <bits/stdc++.h>
#define nmax 1006
#define nnn  5009
#define infinit 10000000
using namespace std;

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

int g[nmax], c[nmax], n;
int d[2][nnn], L0, L1, E;

void Citire()
{
    int i;
    fin >> n >> E;
    for (i=1; i<=n; i++)
        fin >> g[i] >> c[i];
}

void Rezolva()
{
    int i, j;
    L0 = 0; L1 = 1;
    for (i=1; i<=E; i++)
        { d[L0][i] = infinit;
          d[L1][i] = infinit;
        }
    /// initializari
          d[L0][g[1]] = c[1];

    for (i=2; i<=n; i++)
    {
        for (j=0; j<=E; j++)
           {
                d[L1][j] = d[L0][j];
                if (g[i] <= j)  d[L1][j] = min(d[L1][j], d[L0][j - g[i]] + c[i]);
           }
        L0 = 1 - L0;
        L1 = 1 - L1;
    }
}

void Afisare()
{
    int i, j;
    if (d[L1][E] == 0) fout << "-1\n";
    else fout << d[L0][E] << "\n";
}

int main ()
{
    Citire();
    Rezolva();
    Afisare();
    fin.close();
    fout.close();
    return 0;
}