#include <fstream>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");

int n, w;
const int N=1002, W=5002;
int energie[N], cost[N];

void citire() {
    in >> n >> w;
    int i;
    for (i=1; i<=n; i++)
        in >> energie[i] >> cost[i];
}

int costMinim[N][W];

void initializare() {
    int i, j;
    for (i=0; i<=n; i++)
        for (j=1; j<=w; j++)
            costMinim[i][j] = 999999999;
}

void dinamica() {
    int i,e;
    for (i=1; i<=n; i++)
        for (e=1; e<=w; e++) {
            costMinim[i][e] = costMinim[i-1][e];
            if (e-energie[i] >= 0)
                if (costMinim[i][e-energie[i]] + cost[i] < costMinim[i][e])
                    costMinim[i][e] = costMinim[i][e-energie[i]] + cost[i];
        }
}

void afisare() {
    if (costMinim[n][w] == 999999999)
        out <<"-1";
    else
        out << costMinim[n][w];
}

int main()
{
    citire();
    initializare();
    dinamica();
    afisare();
    return 0;
}