#include <fstream>

using namespace std;

ifstream f("energii.in");
ofstream g("energii.out");

int n,cost,max1,i,et,j;
int r[1002][5002],c[1002],e[1002];
int main()
{
    f>>n; f>>cost;
    for(i=1;i<=n;i++)
    f>>c[i]>>e[i];

    for(i=0;i<=n;i++)
        for(j=0;j<=cost;j++)
            r[i][j]=99999999;

    for(i=1;i<=n;i++)
    {
        for(j=1;j<=cost;j++)
        {
            if(j<=c[i])
                r[i][j]=min(e[i],r[i-1][j]);
            else
                r[i][j]=min(r[i-1][j],r[i-1][j-c[i]]+e[i]);
        }
    }
    if(r[n][cost]!=99999999)
        g<<r[n][cost];
    else g<<-1;

    return 0;
}