#include <stdio.h>

#define INF 2000000000
#define en_MAX 15001

int RG[en_MAX];

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 <= W; ++i)
        RG[i] = INF;
    for(k = 1; k <= G; ++k)
    {
        scanf("%d %d",&ce,&cc);
        for(i = W; i >= 1; --i)
        {
            if(RG[i] != INF)
            {
                if(i + ce >= W && RG[i] + cc < RG[W])
                    RG[W] = RG[i] + cc;
                if(i + ce < W && RG[i] + cc < RG[i + ce])
                    RG[i + ce] = RG[i] + cc;
            }
        }
        if(cc < RG[ce])
            RG[ce] = cc;
    }
    if(RG[W] == INF)
        printf("-1\n");
    else
        printf("%d\n",RG[W]);
    return 0;
}