#include <fstream>
#define nmax 1002
#define kmax 1002
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");

int co[nmax][kmax];
int e[nmax];
int v[nmax];

int main()
{
    int n,w;
    fin>>n;
    fin>>w;
    int sum=0;
    for(int i=1;i<=n;i++)
    {
        fin>>e[i]>>v[i];
        sum+=e[i];
    }
    if(sum<w)
    {
        fout<<-1;
    }
    else
    {
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=w;j++)
            {
                co[i][j]=co[i-1][j];
            }
            int con=0;
            if(co[i-1][e[i]]>v[i]||co[i-1][e[i]]==0)
                {co[i][e[i]]=v[i];
                con=1;
                }
            for(int j=1;j<=w;j++)
            {
                if(j==e[i]&&con)
                    continue;
                if(j+e[i]>=w)
                {
                    if(co[i-1][j]&&(co[i-1][j]+v[i]<co[i-1][w]||co[i-1][w]==0))
                    {
                        co[i][w]=co[i-1][j]+v[i];
                    }
                }
                else
                {
                    if(co[i-1][j]&&(co[i-1][j]+v[i]<co[i-1][j+e[i]]||co[i-1][j+e[i]]==0))
                    {
                        co[i][j+e[i]]=co[i-1][j]+v[i];
                    }
                }
            }
        }
        fout<<co[n][w];
    }
    return 0;
}