#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

int N,W,DP[1005][50005],S;
int inf=2000000000;

void ReadAndSolve()
{
    fin>>N>>W;
    for(int i=0;i<=N;i++)
    {
        for(int j=1;j<=W;j++)
        {
            DP[i][j]=inf;
        }
    }
    for(int i=1;i<=N;i++)
    {
       int energie,cost;
       fin>>energie>>cost;
       S=S+cost;
       for(int j=1;j<=W;j++)
       {
          if(j>energie)
           DP[i][j]=min(DP[i-1][j],DP[i-1][j-energie]+cost);
          else
           DP[i][j]=min(DP[i-1][j],cost);
       }
    }
}

int main()
{
    ReadAndSolve();
    if(S<W)
        fout<<"-1";
    else
      fout<<DP[N][W];
    return 0;
}