#include<stdio.h>
#define inf 2000000000
#define min(a,b) (a<b?a:b)

FILE *fin=fopen("energii.in","r"),
    *fout=fopen("energii.out","w");

int N,W,E[5005],C[5005],s[17005],sol;
char uz[5005];

int main(){
    fscanf(fin,"%d %d",&N,&W);

    for(int i=1;i<=N;i++)
        fscanf(fin,"%d %d",&E[i],&C[i]);

    sol=inf;
    for(int i=1;i<=17000;i++)
        s[i]=inf;


    uz[0]=1;
    for(int j=1;j<=N;j++)
        for(int k=W;k>=0;k--)
            if(uz[k]){
                s[k+E[j]]=min(s[k]+C[j],s[k+E[j]]);
                uz[k+E[j]]=1;
                if(k+E[j]>=W)
                    sol=min(sol,s[k+E[j]]);
            }

    if(sol==inf)
        fprintf(fout,"-1\n");
    else
        fprintf(fout,"%d\n",sol);


    fclose(fin);
    fclose(fout);
    return 0;

}