#define INF 0x3f3f3f3f
#include<fstream>
#define nMax 1001
#define eMax 5001
using namespace std;
int N, eNecesar, C[nMax], E[nMax], dp[nMax][eMax], m;

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=0; i<=N; i++)
        for (int j=1; j<=eNecesar; j++)
            dp[i][j] = INF;
    for(int i = 1; i <= N; i++){

        for(int j = 1; j <= eNecesar; j++)
    {

        if(E[i] <= j)
            dp[i][j] = min(dp[i - 1][j], dp[i - 1][j - E[i]] + C[i]);
        else dp[i][j] = min(dp[i - 1][j], C[i]);
          //   g << dp[i][j] << " ";
    }
     //g << '\n';

    }
    if(dp[N][eNecesar] == INF) g <<-1;
    else  g << dp[N][eNecesar];
    return 0;
}