#include <fstream>
#include <algorithm>
#include <cmath>
using namespace std;
ifstream cin("energii.in");
ofstream cout("energii.out");

int a[1005], b[1005], c[5005], i, j,  n, p, s=0, g, w, mx;


int main()
{
    cin>>n>>w;
    mx=0;


    for (i=1; i<=n; ++i)
        cin>>a[i]>>b[i], mx=max(mx, a[i]);

    for (i=1; i<=n; ++i)
    {
        for (j=w; j>0; --j)
        {

            if (c[j])
                if (c[j+a[i]]==0 || c[j+a[i]]> c[j]+b[i] )
                    c[j+a[i]]=c[j]+b[i];
        }

        if (c[j+a[i]]==0 || c[j+a[i]]> c[j]+b[i] )
                    c[j+a[i]]=c[j]+b[i];

    }

    int mn=100000000;

    for (i=w; i<=w+mx; ++i)
        if (c[i]) mn=min(mn, c[i]);

    if (mn==100000000) cout<<-1;
            else cout<<mn;

    return 0;
}