#include <iostream>
#include <fstream>
#include <limits>
#define NMAX 1010
using namespace std;

ifstream f("energii.in");
ofstream g("energii.out");

unsigned long a[NMAX][NMAX];
int e[NMAX],c[NMAX];
int emin,n,esum;

int main()
{
    f >> n >> emin;
    for(int i=0; i<n; i++)
    {
        f >> e[i] >> c[i];
        a[0][i+1] = c[i];
        a[i][0] = 0;
        esum+=e[i];
    }

    if(esum >= emin)
    {
        for(int i=1; i<=n; i++)
            for(int j=1; j<=emin; j++)
                a[i][j] = ULONG_MAX;

        for(int i=1; i<=n; i++)
        {
            for(int w = 1; w<= emin; w++)
            {
                a[i][w] = min(a[i-1][w],a[i-1][w-c[i-1]] + c[i-1]);
                if(e[i-1] >= emin && a[i][w] == 0) a[i][w] =  (unsigned long )c[i-1];

            }
        }

        g << a[n][emin];
    }
    else
        g << -1;

    return 0;
}