#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define rng(a) a.begin(),a.end()
#define rrng(a) a.rbegin(),a.rend()
#define isin(x,l,r) ((l) <= (x) && (x) < (r))
#define pb push_back
#define eb emplace_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcountll
#define uni(x) x.erase(unique(rng(x)),x.end())
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
#define show(x) cerr<<#x<<" = "<<x<<endl;
#define PQ(T) priority_queue<T,v(T),greater<T> >
#define bn(x) ((1<<x)-1)
#define dup(x,y) (((x)+(y)-1)/(y))
#define newline puts("")
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
typedef long long int ll;
typedef unsigned uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef tuple<int,int,int> T;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
typedef vector<T> vt;
int getInt(){int x;scanf("%d",&x);return x;}
template<typename T>istream& operator>>(istream&i,v(T)&v){rep(j,sz(v))i>>v[j];return i;}
template<typename T>string join(const v(T)&v){stringstream s;rep(i,sz(v))s<<' '<<v[i];return s.str().substr(1);}
template<typename T>ostream& operator<<(ostream&o,const v(T)&v){if(sz(v))o<<join(v);return o;}
template<typename T1,typename T2>istream& operator>>(istream&i,pair<T1,T2>&v){return i>>v.fi>>v.se;}
template<typename T1,typename T2>ostream& operator<<(ostream&o,const pair<T1,T2>&v){return o<<v.fi<<","<<v.se;}
template<typename T>bool mins(T& x,const T&y){if(x>y){x=y;return true;}else return false;}
template<typename T>bool maxs(T& x,const T&y){if(x<y){x=y;return true;}else return false;}
template<typename T>ll suma(const v(T)&a){ll res(0);for(auto&&x:a)res+=x;return res;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#define dame { puts("-1"); return 0;}
#define yn {puts("Yes");}else{puts("No");}
const int MX = 200005;
#include <atcoder/all>
using namespace atcoder;

int n, n3;
vi a, b;

bool f(int l, int r) {
  two_sat t(n);
  vvi js(n);
  srep(i,l,n3-r) js[b[i]].pb(i);
  vvi ls(n);
  vvi rs(n);
  rep(i,l) ls[b[i]].pb(i);
  rep(i,r) rs[b[n3-1-i]].pb(i);
  vvi is(n);
  rep(i,n3) is[a[i]].pb(i);

  vi x(n3,-1);
  vi es;
  vi tl, tr;
  rep(i,n) {
    if (sz(js[i]) == 3) {
      rep(j,3) x[is[i][j]] = js[i][j];
    } else if (sz(js[i]) == 2) {
      rep(j,2) x[is[i][j*2]] = js[i][j];
    } else if (sz(js[i]) == 1) {
      if (sz(ls[i]) == 2) {
        x[is[i][2]] = js[i][0];
      } else if (sz(rs[i]) == 2) {
        x[is[i][0]] = js[i][0];
      } else {
        es.pb(i);
      }
    } else { // 0
      if (sz(ls[i]) == 0) return false;
      if (sz(rs[i]) == 0) return false;
      if (sz(ls[i]) == 2) tl.pb(i);
      else tr.pb(i);
    }
  }

  vi y = x;
  int mx = 0;
  rep(i,n3) {
    if (x[i] == -1) {
      x[i] = mx;
      continue;
    }
    if (x[i] < mx) return false;
    mx = x[i];
  }
  int mn = n3-1;
  drep(i,n3) {
    if (y[i] == -1) {
      y[i] = mn;
      continue;
    }
    if (y[i] > mn) return false;
    mn = y[i];
  }

  rep(ei,sz(es))rep(ej,sz(es)) if (ei != ej) {
    int i = es[ei], j = es[ej];
    if (ls[i][0] < ls[j][0] && rs[i][0] > rs[j][0]) {
      t.add_clause(i,true,j,false);
    }

    int pi = js[i][0], pj = js[j][0];
    if (pi < pj) {
      rep(bi,2)rep(bj,2) {
        int qi = is[i][bi*2], qj = is[j][bj*2];
        if (qi > qj) t.add_clause(i,bi,j,bj);
      }
    }
  }

  // cerr<<tl<<" / "<<tr<<endl;

  rep(ei,sz(es)) {
    int i = es[ei];
    int pi = js[i][0];
    int li = is[i][0], ri = is[i][2];
    if (x[li] > pi || pi > y[li]) t.add_clause(i,false,i,false);
    if (x[ri] > pi || pi > y[ri]) t.add_clause(i,true,i,true);

    li = ls[i][0]; ri = rs[i][0];
    for (int j : tl) {
      int lj = ls[j][0], rj = rs[j][0];
      if (li < lj && rj < ri) t.add_clause(i,true,i,true);
    }
    for (int j : tr) {
      int lj = ls[j][0], rj = rs[j][0];
      if (li > lj && rj > ri) t.add_clause(i,false,i,false);
    }
  }

  for (int i : tl) for (int j : tr) {
    int li = ls[i][0], ri = rs[i][0];
    int lj = ls[j][0], rj = rs[j][0];
    if (lj < li && ri < rj) return false;
  }

  return t.satisfiable();
}

int main() {
  n;
  scanf("%d",&n);
  n3 = n*3;
  a = b = vi(n3);
  cin>>a>>b;
  rep(i,n3) --a[i];
  rep(i,n3) --b[i];
  int ans = INF;
  rep(l,n3)rep(r,n3-l) {
    if (f(l,r)) {
      // cerr<<l<<" "<<r<<endl;
      mins(ans, l+r);
    }
  }
  if (ans == INF) ans = -1;
  cout<<ans<<endl;
  return 0;
}






















Measured memory_bytes: 3792