#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

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

int nrGen,energMax,generator,costG,i,j;

int main(){

    fin >> nrGen >> energMax;
    vector<int> cost(energMax + 1,10010);
    for(i=0;i<nrGen;i++)
    {
        fin >> generator >> costG;
        for(j=energMax;j>=0;j--)
        {
            if(j<=generator)
                cost[j] = min(cost[j],costG);
            else
                cost[j] = min(cost[j],cost[j-generator]+costG);
        }
    }
    if(cost[energMax]==10010)
        fout << "-1";
    else
        fout << cost[energMax];
    return 0;
} ///