#include <iostream>
#include <fstream>
#include <limits.h>
#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;
//          unsolved
int main()
{
    f >> n >> emin;
    for(int i=0; i<n; i++)
    {
        f >> e[i] >> c[i];
        esum+=e[i];
    }

    for(int i=0;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] = a[i-1][w];
            if(w >= e[i-1])    a[i][w] = min(a[i][w],a[i][w-e[i-1]] + c[i-1]);
            else a[i][w] = min(a[i][w],(unsigned long)c[i-1]);
        }
    }
    if(a[n][emin] == ULONG_MAX) g << -1;
    else g << a[n][emin];
    return 0;
}