#include <fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int g, w,  produce[1002], costa[1002], rez[5002];

int main()
{
    fin>>g>>w;

    rez[0]=1;

    for(int i=1;i<=5001;i++)
        rez[i]=2000000000;

    for(int i=1;i<=g;i++)
    {
        fin>>produce[i]>>costa[i];


        for(int j=w+produce[i]-1; j>=produce[i]; j--)
            if(rez[j-produce[i]]+costa[i]<rez[i])
            {
            if(j>=w)
            rez[w]=rez[j-produce[i]]+costa[i];
            else
            rez[j]=rez[j-produce[i]]+costa[i];
            }
    }

    fout<<rez[w]-1;

    return 0;
}