#include <fstream>
using namespace std;

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

int eg[10005], cg[10005], dp[10005], emax;

int main(){
    int g;
    fin >> g;
    int w;
    fin >> w;
    for(int i = 1; i <= g; i++){
        fin >> eg[i];
        fin >> cg[i];
    }
    dp[0] = 1;
    for(int i = 1; i <= g; i++){
        for(int j = emax; j >= 0; j--){
            if(dp[j] != 0) {
                int ne = min(j + eg[i], w);
                if (dp[ne] != 0)
                    dp[ne] = min(dp[ne], dp[j] + cg[i]);
                else{
                    dp[ne] = dp[j] + cg[i];
                    emax = max(max(ne, emax), w);
                }
            }
        }
    }
    if (dp[w] != 0)
        fout << dp[w] - 1;
    else
        fout << -1;
}