#include <iostream>
#include <fstream>
#define NMAX 1000
#define NMAX2 15000
#define maxim 1e9
using namespace std;
int n, s, ras=maxim, i, j, en[NMAX+1], cg[NMAX+1], d[NMAX2+1];
int main()
{
    ifstream cin("energii.in");
    ofstream cout("energii.out");
    cin>>n>>s;
    for(i=1; i<=n; i++)
        cin>>en[i]>>cg[i];
    for(i=1; i<=NMAX2; i++)
        d[i]=maxim;
    for(i=1; i<=n; i++)
        for(j=s; j>=0; j--)
            d[j+en[i]]=min(d[j]+cg[i],d[j+en[i]]);
    for(i=s; i<=NMAX2; i++)
        ras=min(ras,d[i]);
    if(ras==maxim)
        cout<<-1<<'\n';
    else
        cout<<ras<<'\n';
    return 0;
}