#include <fstream>
#define INF 2000000001
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int n,j,gmax,i,e[1011],c[1011],d[1011][5011];
int main()
{
    f>>n;
    f>>gmax;
    for(i=1;i<=n;i++)
        f>>e[i]>>c[i];
    for(i=0;i<=n;i++)
        for(j=0;j<=gmax;j++)
            d[i][j]=INF;
    for(i=1;i<=n;i++)
        for(j=1;j<=gmax;j++)
            if(j<=e[i])
                d[i][j]=min(d[i-1][j],c[i]);
            else
                d[i][j]=min(d[i-1][j],d[i-1][j-e[i]]+c[i]);
    if(d[n][gmax]==INF)
        g<<-1;
    else
        g<<d[n][gmax];
    return 0;
}