#include<fstream>
#define INF 999999999
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int i,n,j,s,d[1010][5010];
struct kkk{int x,y;}a[1010];
int main()
{
    f>>n>>s;
    for(i=1;i<=n;++i)
    f>>a[i].x>>a[i].y;
    for(i=0;i<=n;++i)
    for(j=0;j<=s;++j)
    d[i][j]=INF;
    for(i=0;i<=n;++i)
    d[i][0]=0;
    for(i=1;i<=n;++i)
    for(j=0;j<=s;++j)
    if(j<a[i].x)
    d[i][j]=min(d[i-1][j],a[i].y);
    else
    d[i][j]=min(d[i-1][j],d[i-1][j-a[i].x]+a[i].y);
    if(d[n][s]==INF)
    g<<-1<<'\n';
    else
    g<<d[n][s]<<'\n';
    return 0;
}