#include<bits/stdc++.h>
#define ll long long
#define INF 300000000000
#define EPS 0.000000001
#define f first
#define s second
using namespace std;
ll n;
ll dp[3002][4];
ll srr[3002];
ll crr[3002];

ll solve(ll ind, ll x,ll num){
    if(x>=3){
        return 0;
    }
    if(ind>=n){
        return INF;
    }
    // cout<<ind<<" "<<x<<" "<<num<<endl;
    // cout<<"DFD"<<endl;
    if(dp[ind][x]!=-1)
        return dp[ind][x];
    ll A=INF,B=INF;
    if(srr[ind]>num){
        A=solve(ind+1,x+1,srr[ind])+crr[ind];
    }
    B=solve(ind+1,x,num);
    dp[ind][x]=min(A,B);
    // cout<<ind<<" "<<x<<endl;
    // cout<<"ans "<<A<<" "<<B<<" "<<dp[ind][x]<<endl;
    return dp[ind][x];
}
int main(){
    cin>>n;
    for(ll i=0;i<n;i++)
        cin>>srr[i];
    for(ll i=0;i<n;i++)
        cin>>crr[i];
    for(ll i=0;i<3002;i++)
        for(ll j=0;j<4;j++)
            dp[i][j]=-1;
    ll ans=solve(0,0,-1);
    // for(ll i=0;i<n;i++){
    //  for(ll j=0;j<3;j++){
    //      cout<<dp[i][j]<<" ";
    //  }
    //  cout<<endl;
    // }
    if(ans==INF)
        cout<<-1<<endl;
    else
    cout<<ans<<endl;
    return 0;
}