#include <fstream>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
const int N=5001;
int v[N];
int main()
{
    ///suma min pt. e>=s
    int n,s,e,c;
    in>>n>>s;
    for(int i=1;i<=s;i++)
        v[i]=N*N;
    for(int i=1;i<=n;i++){
        in>>e>>c;
        for(int j=s;j;j--){
            if(e>=j)
                v[j]=min(v[j],c);
            else if(v[j=e]<N*N)
                v[j]=min(v[j],v[j-e]+c);
        }
    }
    in.close();
    if(v[s]<N*N)
        out<<v[s]<<"\n";
    else
        out<<"-1\n";
    out.close();
    return 0;
}