#include <stdio.h>

int RG[10001];

int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    int G,W,ce,cc,mx = 0,k,i,j;
    scanf("%d\n%d\n",&G,&W);
    for(i = 1; i <= 10000; ++i)
        RG[i] = 20000000;
    for(k = 1; k <= G; ++k)
    {
        scanf("%d %d",&ce,&cc);
        for(i = mx; i >= 1; --i)
        {
            if(RG[i] > 0 && i + ce <= 10000 && RG[i] + cc < RG[i + ce] )
                {
                    RG[i + ce] =  RG[i] + cc;
                    if(i + ce > mx)
                        mx = i + ce;
                }
        }
            if(RG[ce] != 0 && RG[ce] > cc)
            {
                RG[ce] = cc;
                if(ce > mx)
                    mx = ce;
            }
    }
    int minim = 200000000;
    for(k = W; k <= 10000; ++k)
    {
        if(RG[k] < minim)
            minim = RG[k];
    }
    if(minim == 200000000)
        printf("-1\n");
    else
        printf("%d\n",minim);
    return 0;
}