# include <fstream>
# define INF 5001
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int f[10010],e[1002],s,c[1002],n,lim,i,sf,j,minim,sol;
int main () {
    fin>>n>>lim;
    for(i=1;i<=n;i++){
        fin>>e[i]>>c[i];
        s=s+e[i];
    }
    for(i=1;i<=s;i++){
        f[i]=INF;
    }
    f[0]=0;
    sol=INF;
    for(i=1;i<=n;i++){
        for(j=s;j>=0;j--){
            if(f[j]!=INF){
                f[j+e[i]]=min(f[j+e[i]],f[j]+c[i]);
                if(j+e[i]>=lim){
                    sol=min(sol,f[j+e[i]]);
                }
            }
        }
    }
    fout<<sol;
    fin.close();
    fout.close();
    return 0;
}