#include <iostream>
#include <fstream>
#include <vector>
#define gmax 5005
#define nmax 1005
using namespace std;

int n, gen;
int ener[nmax][gmax];
int eg[nmax], cg[nmax];

void read()
{
    ifstream f("energii.in");
    f >> n >> gen;
    for(int i=1; i<=n; ++i)
    {
        f >> eg[i] >> cg[i];
    }
    f.close();

}

void solve()
{
    for(int i=0; i<=n; ++i)
    {
        for(int k=0; k<=gen; ++k)
        {
            ener[i][k] = 10005;
        }
    }

    for(int i=1; i<=n; ++i)
    {
        for(int k=1; k<=gen; ++k)
        {
            if(eg[i]<k)
            ener[i][k] = min(ener[i-1][k], ener[i-1][k-eg[i]] + cg[i]);
            else
            ener[i][k] = min(ener[i-1][k], cg[i]);
        }
    }
}

void out()
{
    ofstream g("energii.out");
    if(ener[n][gen]==10005)
    g << -1 << '\n';
    else
    g << ener[n][gen] << '\n';
    g.close();
}

int main()
{
    read();
    solve();
    out();
    return 0;
}