#include <iostream>
#include <fstream>
using namespace std;
int g,w,e[1001],c[1001],d[100001];
int const oo=200000000;
ifstream fin ("energii.in");
ofstream fout ("energii.out");
int cost ()
{
    int i,j;
    for (i=1;i<=g;i++)
        for (j=e[i];j<=w;j++)
            d[j]=min(d[j],d[j-e[i]]+c[i]);
    return d[w];
}
int main()
{
    int i;
    fin>>g>>w;
    for (i=1;i<=g;i++)
        fin>>e[i]>>c[i];
    for (i=1;i<=1001;i++)
        d[i]=oo;
    fout<<cost();
    fin.close();
    fout.close();
    return 0;
}