#include<fstream>
#define nMax 1001
#define eMax 5001
using namespace std;
int N, eNecesar, C[nMax], E[nMax], dp[nMax][eMax],mn=9999999;

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

int main()
{
    f >> N >> eNecesar;
    for(int i = 1; i <= N; i++)
        f >> E[i] >> C[i];
    for(int i = 1; i <= N; i++){
        for(int j = 0; j <= eNecesar; j++)
    {
        if(E[i] > eNecesar) E[i] = eNecesar;
        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(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] << " ";
    }
    // g << '\n';
     if(dp[i][eNecesar] < mn && dp[i][eNecesar] != 0)
        mn = dp[i][eNecesar];
    }
    if(mn == 9999999) g<< -1;
    else
    g << mn;

    return 0;
}