#include<fstream>
#define nMax 1001
#define eMax 5001
using namespace std;
int N, eNecesar, C[nMax], E[nMax], dp[nMax][eMax],mn=500150010, m;

ifstream f("energii.in");
ofstream g("energii.out");
void sortez(int N)
{
    int aux = 0;
    for(int i = 1; i < N; i++)
    for(int j = i+1; j <= N; j++)
    {
        if(E[i] > E[j])
        {
            aux = E[i];
            E[i] = E[j];
            E[j] = aux;
            aux = C[i];
            C[i] = C[j];
            C[j] = aux;
        }
    }
}
int main()
{

    f >> N >> eNecesar;
    for(int i = 1; i <= N; i++)
        f >> E[i] >> C[i];
    sortez(N);
    for(int i = 1; i <= N; i++){
             if(E[i] > eNecesar) E[i] = eNecesar;
            if(E[i] <= eNecesar) m = eNecesar + E[i] - 1;
             else  m = E[i];

        for(int j = 0; j <= m; j++)
    {

        dp[i][j] = dp[i - 1][j];
        if(E[i] == j){
         dp[i][j] = C[i];
        if(dp[i - 1][j] != 0)dp[i][j] = min(dp[i-1][j], dp[i][j]);
        }
        if(j <= eNecesar){
          if(dp[i - 1][j - E[i]] != 0 && E[i] < j){
            dp[i][j] = dp[i - 1][j - E[i]] + C[i];
           if(dp[i-1][j] != 0) dp[i][j] = min(dp[i][j], dp[i - 1][j]);

            }
             //g << dp[i][j] << " ";
        }

        else
        {
           if(dp[i - 1][j - E[i]] != 0 && E[i] < j){
            dp[i][eNecesar] = min(dp[i - 1][j - E[i]] + C[i], dp[i][eNecesar]);
           if(dp[i-1][eNecesar] != 0) dp[i][eNecesar] = min(dp[i][eNecesar], dp[i - 1][eNecesar]);

            }
        }


    }
   //  g << '\n';
     if(dp[i][eNecesar] < mn && dp[i][eNecesar] != 0)
        mn = dp[i][eNecesar];
    }
    if(mn == 500150010) g<< -1;
    else
    g << mn;

    return 0;
}