#include<fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int main(){
    int v[5002]={0};
    int n, energy, e, c;
     fin>>n>>energy;
    for(int i=1; i<=energy; i++)
        v[i]=5002*5002;
    for(int i=1; i<=n; i++){
        fin>>e>>c;
        for(int j=energy; j>=1; j--){
            if(e>=j)
                v[j]=min(v[j], c);
            else if(v[j-e]<5002*5002)
                v[j]=min(v[j], v[j-e]+c);
        }
    }
    if(v[energy]<5002*5002) fout<<v[energy];
    else fout<<"-1";
    return 0;
}