#include <fstream>

using namespace std;
ifstream in ("energii.in");
ofstream out ("energii.out");
int v[10000005];
int main()
{
    long long g,w,eg,i,cons,sum=0,j,min=999999999;
    in>>g>>w;
    for(i=1;i<=g;i++)
    {
        in>>eg>>cons;
        sum+=eg;
        for(j=sum-eg;j>0;j--)
        {
            if(v[j]!=0 && (v[j+eg]>v[j]+cons || v[j+eg]==0))
               v[j+eg]=v[j]+cons;
        }
        if(v[eg]>cons || v[eg]==0)
            v[eg]=cons;
    }
    for(i=w;i<=10001;i++)
        {
            if(v[i]<min && v[i]!=0)
            min=v[i];
        //    out<<v[i]<<"\n";
        }
    out<<min;
    return 0;
}