source_code: import java.util.*;
  
  import java.lang.*;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.*;
   
  public class Main {
          
      public static void main(String[] args) throws Exception{
          FastReader sc=new FastReader(); 
          OutputStream outputStream = System.out;
          PrintWriter out = new PrintWriter(outputStream);
          int n=sc.nextInt();
          int[] font=new int[n];
          int[] cost=new int[n];
          for(int i=0;i<n;i++) {
              font[i]=sc.nextInt();
          
          }
          for(int i=0;i<n;i++) {
              cost[i]=sc.nextInt();
          }
          int[] dou= new int[n];
          for(int i=0;i<n;i++) {
              int min=Integer.MAX_VALUE;
              for(int j=0;j<i;j++) {
                  if(font[j]<font[i]) {
                      if(min>cost[i]+cost[j]) {
                          min=cost[i]+cost[j];
                      }
                  }
              }
              dou[i]=min;
          }
          int ans=Integer.MAX_VALUE;
          for(int i=0;i<n;i++) {
              int min=Integer.MAX_VALUE;
              for(int j=0;j<i;j++) {
                  if(dou[j]!=Integer.MAX_VALUE && font[j]<font[i]) {
                      if(min>dou[j]+cost[i]) {
                          min=dou[j]+cost[i];
                      }
                  }
              }
              if(min<ans) {
                  ans=min;
              }
          }
          if(ans==Integer.MAX_VALUE) {
              System.out.println(-1);
          }
          else {
              System.out.println(ans);
          }
      }
  }
  
  class FastReader 
  { 
      BufferedReader br; 
      StringTokenizer st; 
   
      public FastReader() 
      { 
          br = new BufferedReader(new
                   InputStreamReader(System.in)); 
      } 
   
      String next() 
      { 
          while (st == null || !st.hasMoreElements()) 
          { 
              try
              { 
                  st = new StringTokenizer(br.readLine()); 
              } 
              catch (IOException  e) 
              { 
                  e.printStackTrace(); 
              } 
          } 
          return st.nextToken(); 
      } 
   
      int nextInt() 
      { 
          return Integer.parseInt(next()); 
      } 
   
      long nextLong() 
      { 
          return Long.parseLong(next()); 
      } 
   
      double nextDouble() 
      { 
          return Double.parseDouble(next()); 
      } 
   
      String nextLine() 
      { 
          String str = ""; 
          try
          { 
              str = br.readLine(); 
          } 
          catch (IOException e) 
          { 
              e.printStackTrace(); 
          } 
          return str; 
      } 
  } 