#include <stdio.h>
using namespace std;

int c[100001], energie[10001], cost[10001];
int n, i, j, k;
int Min = 2000000;
long int suma, S;

int main ()
{
    FILE *f = fopen ("energii.in","r");
    FILE *g = fopen ("energii.out","w");
    fscanf (f,"%d", &n);
    fscanf (f,"%ld", &S);
    for (i=1; i<=n; ++i)
    {
        fscanf (f,"%d %d", &energie[i], &cost[i]);
        suma += energie[i];
    }

    if (S > suma)
    {
        fprintf (g,"-1");
        return 0;
    }

    S *= 2;
    for (i=1; i<=S; ++i)
        c[i] = 2000000;

    for (i=1; i<=n; ++i)
        for (j=S; j>=0; --j)
            if (energie[i] <= j && cost[i] + c[j-energie[i]] < c[j])
                c[j] = cost[i] + c[j-energie[i]];

    /*for (i=1; i<=S; ++i)
        printf ("%d ", c[i]);*/
    for (i=S; i>=S/2; --i)
        if (c[i] < Min)
            Min = c[i];

    fprintf (g,"%d", Min);

    fclose(g);
    fclose(f);
    return 0;
}