#include <iostream>
#include <fstream>
#define Gmax 10001
#define oo 100000000
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int E[Gmax],G,w,C[Gmax],DP[Gmax];

void read()
{
    fin>>G>>w;
    int i;
    for(i=1;i<=G;i++)
        fin>>E[i]>>C[i];
}
//DP[i]=costul minim pt a obtine o energie=i

void solve()
{
    int i,j;
    for(i=1;i<=w;i++)
            DP[i]=oo;

    for (i=1;i<=G;i++)
        for (j=w;j>=0;j--)
            if (j>=E[i])
               {
                   if(DP[j]>DP[j-E[i]]+C[i]) DP[j]=DP[j-E[i]]+C[i];
               }

        else DP[j]=min(DP[j], C[i]);

    if (DP[w]!=oo) fout<<DP[w];
        else fout<<"-1";
}
int main()
{
    read();
    solve();
    return 0;
}