#include <iostream>
#include <cstdio>
using namespace std;
int p[1007],c[1007],d[1007][1007],n,g;
int main(){
    int i,j,sum;
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    scanf("%d%d",&n,&g);
    for(i=1;i<=n;i++)
     scanf("%d%d",&p[i],&c[i]);
    for(i=1;i<=g;i++) d[0][i]=999999;
     for(i=1;i<=n;i++)
      for(j=1;j<=g;j++)
       {
              d[i][j]=d[i-1][j];
              sum=d[i][j];
              if(sum >= j){
              if(d[i-1][j-p[i]]+c[i] < d[i][j])
                sum=sum-p[i-1]+p[i];
              d[i][j] = min(d[i][j],d[i-1][j-p[i]]+c[i]);}
       }
//     for(i=1;i<=n;i++){
//        for(j=1;j<=g;j++)
//         printf("%d ",d[i][j]);
//        printf("\n");
//     }
    if(d[n][g] == 999999) printf("-1\n");
    else
  printf("%d\n",d[n][g]);
    return 0;
}