#include <fstream>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int c[1001];
#define inf 987654321
int main()
{
    int n,et;
    f>>n;
    f>>et;
    int i,j;
    for(i=1;i<=et;i++)
        c[i]=inf;
    for(i=1;i<=n;i++)
    {
        int cost,e;
        f>>e>>cost;
        for(j=et;j>=e;--j)
        {
            if(c[j]>c[j-e]+cost)
                c[j]=c[j-e]+cost;
        }
        for(int ii=e;ii>=1;--ii)
            if(c[ii]>cost)
                c[ii]=cost;

    }
    if(c[et]!=inf)
        g<<c[et];
    else
        g<<"-1";
    return 0;
}