#include <bits/stdc++.h>
#define NRMAX 1001
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int DP[NRMAX];
int main()
{
    int n,P,i,j,cost,en;
    fin>>n>>P;
    for(i = 1 ; i <= n; i++)
    {
        fin>>en>>cost;
        for(j = P; j >= 1; j--)
        {
            if(DP[j] != 0)
            {
                if(j + en >= P)
                {
                    if(DP[P] == 0)
                    {
                        DP[P] = DP[j] - cost;
                    }
                    else
                    {
                        DP[P] = max(DP[P],DP[j]-cost);
                    }
                }
                else
                {
                    if(DP[j+en] == 0)
                    {
                        DP[j+en] = DP[j] - cost;
                    }
                    else
                    {
                        DP[j+en] = max(DP[j+en],DP[j]-cost);
                    }
                }
            }
        }
        if(DP[en] != 0)
            DP[en] = max(DP[en],-cost);
        else
            DP[en] = -cost;
    }
    if(DP[P] == 0)
    {
        fout<<"-1"<<endl;
    }
    else
    {
        fout<<-DP[P]<<endl;
    }
    return 0;
}