#include <cstdio>
#define MAXG 1000
#define MAXW 10000000
#define INF 1000000000
int mat[2][MAXW+1],E[MAXG],C[MAXG];
inline int min(int a,int b){
    if(a<b) return a;
    return b;
}
int main(){
    FILE*fi,*fout;
    int i,j,n,G,W,s=0;
    fi=fopen("energii.in" ,"r");
    fout=fopen("energii.out" ,"w");
    fscanf(fi,"%d%d" ,&G,&W);
    for(i=0;i<G;i++){
       fscanf(fi,"%d%d" ,&E[i],&C[i]);
       s+=E[i];
    }
    for(i=0;i<2;i++)
      for(j=1;j<=s;j++)
         mat[i][j]=INF;
    for(i=1;i<=E[0];i++)
       mat[0][i]=C[0];
    for(i=1;i<G;i++){
        for(j=1;j<=s;j++)
          if(E[i]>j)
             mat[i&1][j]=mat[1-i&1][j];
          else
             mat[i&1][j]=min(mat[1-i&1][j],mat[1-i&1][j-E[i]]+C[i]);
    }
    while(W<=s&&mat[1-G&1][W]==INF)
       W++;
    if(W==s+1)
      fprintf(fout,"-1");
    else
      fprintf(fout,"%d" ,mat[1-G&1][W]);
    fclose(fi);
    fclose(fout);
    return 0;
}