#include <iostream>
#include <fstream>
#define inf 0x3f3f3f3f
#define maxN 1001
#define maxG 5001

using namespace std;

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

int n, G, W[maxN], C[maxN], Op[maxG];

int main() {
    fin >> n >> G;
    for (int i = 1; i <= n; ++i) {
        fin >> W[i] >> C[i];
    }
    for (int i = 1; i <= G; ++i) {
        Op[i] = inf;
    }
    for (int i = 1; i <= n; ++i) {
        for (int j = G; j >= 1; --j) {
            if (W[i] > j) {
                Op[j] = min(Op[j], C[i]);
            }
            else {
                Op[j] = min(Op[j], Op[j-W[i]] + C[i]);
            }
        }
    }
    if (Op[G] == inf)
        fout << "-1";
    else
        fout << Op[G];
}