#include<fstream>

using namespace std;

int e[10001], c[10001];
int cost[15002];
//cost[j] = costul minim necesar pt.  produce energia j
int main()
{
    ifstream in("energii.in");
    ofstream out("energii.out");

    int g,w,i,j;
    int emax=0;

    in>>g>>w;
    for(i=1;i<=g;i++)
    {
        in>>e[i]>>c[i];
        if(e[i]>emax) emax = e[i];
    }
    for(j=1; j<=w+emax; j++)
        cost[j] = 10002;

    for(i=1;i<=g;i++)
    {
        for (j = w - 1; j >= 0; j--)
            if (cost[j]!=10002 && cost[j] + c[i] < cost[j + e[i]])
                cost[j+e[i]] = cost[j] + c[i];
    }
    int r = 10002;

    for(i=w;i<=w+emax;i++)
        if(cost[i]<r) r=cost[i];
    if(r==10001) out<<"-1";
    else out<<r;


    return 0;
}