#include <cstdio>

#define MAX 5050
#define INF 2000000000

using namespace std;

int v[MAX];
int nrGen, power;

void citSolve()
{
    freopen("energii.in", "r", stdin);
    int energy, cost;
    scanf("%d\n%d\n", &nrGen, &power);
    for(int i = 1; i <= power; i++)
    {
        v[i] = INF;
    }
    for(int i = 1; i <= nrGen; i++)
    {
        scanf("%d %d\n", &energy, &cost);
        for(int j = power; j >= 0; j--)
        {
            if(v[j] != INF)
            {
                if(j + energy >= power && v[power] > v[j] + cost)
                {
                    v[power] = v[j] + cost;
                }
                if(j + energy < power && v[j + energy] > v[j] + cost)
                {
                    v[j + energy] = v[j] + cost;
                }
            }
        }
    }
    fclose(stdin);
}

void afisare()
{
    freopen("energii.out", "w", stdout);
    if(v[power] == INF)
    {
        printf("%d", -1);
    }
    else
    {
        printf("%d", v[power]);
    }
    fclose(stdout);
}

int main()
{
    citSolve();
    afisare();
    return 0;
}