#include <fstream>
#include <algorithm>
#include <vector>
#define INF 0x3FFFFFFF
using namespace std;

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

int n;

long long s;


long long sol[5005];

int main()
{
    fin>>n>>s;

    for(int i=1;i<=s;i++)
        sol[i] = INF;
    for(int i=1;i<=n;i++)
    {
        long long energy,cost;
        fin>>energy>>cost;
        for(int j = s; j>=0;j--)
            if(sol[j]!=INF)
                sol[min(s,j + energy)] = min(sol[min(s,j + energy)] , sol[j]+cost);
    }
    if(sol[s]==INF)
        fout<<-1;
    else
        fout<<sol[s];
}