#include <fstream>
using namespace std;

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

int v[5005];

int main(){

    int n,m,x,y,i,j;
    fin>>n>>m;
    for(i = 1; i <= m; i++) v[i] = 5000000;
    for(i = 1; i <= n; i++){
        fin>>x>>y;
        for(j = m; j >= 0; j--){
            if(j+x < m){
                v[j+x] = min(v[j+x],v[j]+y);
            }
            else{
                v[m] = min(v[m],v[j]+y);
            }
        }
    }
    if(v[m] != 5000000) fout<<v[m];
    else fout<<-1;

}