#include <fstream>

using namespace std;

int a[1004][5005],gr[1004],c[1005];
int n,sol,i,j;

int main()
{
    ifstream f("energii.in");
    ofstream g("energii.out");
    f>>n>>sol;
    for(i=1; i<=n; i++)
        f>>gr[i]>>c[i];
    for(i=0; i<=n; i++)
        for(j=1; j<=sol; j++)
            a[i][j]=2000000000;
    for(i=1; i<=n; i++)
        for(j=1; j<=sol; j++)
            if(gr[i]<=j)
                a[i][j]=min(a[i-1][j],a[i-1][j-gr[i]]+c[i]);
            else
                a[i][j]=min(a[i-1][j],c[i]);
    if(a[n][sol]==2000000000)
        g<<"-1"<<"\n";
    else
        g<<a[n][sol]<<"\n";
    f.close();g.close();
    return 0;
}