#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

int inf,n,g,x,y,i,j,v[5001];
#define inf 2000000
int main()
{
    fin>>n>>g;
    for (i=1;i<=g;i++)
        v[i]=inf;

    for(i=1;i<=n;i++)
    {
        fin>>x>>y;

        for(j=g;j>=0;j--)
            if(j<=x)
                v[j]=min(v[j],y);
            else
                v[j]=min(v[j],v[j-x]+y);
    }
    if (v[g]!=inf)
        fout<<v[g];
    else
        fout<<"-1";

    fin.close();
    fout.close();
    return 0;
}