#include <iostream>
#include<fstream>
#include<algorithm>
using namespace std;
int n,w,eg[1005],cg[1005],d[1005][5005];
void Citire()
{
    int i;
    ifstream fin("energii.in");
    fin>>n>>w;
    for(i=1;i<=n;i++)
        fin>>eg[i]>>cg[i];
    fin.close();
}
void Initializare()
{
    int i,j;
    for(i=0;i<=n;i++)
        for(j=1;j<=w;j++)
            d[i][j]=2000000000;
}
void Solve()
{
    int i,j;
    Initializare();
    //d[i][j]=min(d[i-1][j], d[i-1][j-eg[i]] + cg[i]);
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=w;j++)
        {
            if(j>=eg[i])
                d[i][j]=min(d[i-1][j], d[i-1][j-eg[i]] + cg[i]);
            else
                d[i][j]=min(d[i-1][j],cg[i]);
        }
    }

    ofstream fout("energii.out");
    if(d[n][w]==2000000000)
        fout<<"-1\n";
    else fout<<d[n][w]<<"\n";
    fout.close();
}
int main()
{
    Citire();
    Solve();
    return 0;
}