#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define REP(a,b) for(int a=0;a<(b);++a)
#define REP1(i,n) for(int i=1;i<=(n);++i)
#define debug(x) cerr<<#x<<": "<<x<<'\n'
#define all(x) (x).begin(),(x).end()
#define YES() printf("YES\n")
#define NO() printf("NO\n")
#define isYES(x) printf("%s\n",(x) ? "YES" : "NO")
#define Yes() printf("Yes\n")
#define No() printf("No\n")
#define isYes(x) printf("%s\n",(x) ? "Yes" : "No")
#define isPossible(x) printf("%s\n",(x) ? "Possible" : "Impossible")
#define SZ(x) ((int)(x).size())
#define pb push_back
#define mp make_pair
#define INF (1<<29)

// const long long INF = 1LL<<62;

#define Sp(p) cout<<setprecision(25)<< fixed<<p<<endl
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
#define pie 3.14159265358979323846
using namespace std;
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
typedef pair<int, P> PP;
typedef pair<ll, LP> LPP;
template<class T=int>
T in(){T x;cin>>x;return (x);}
template<class T>
void print(T& x){cout<<x<<'\n';}

const int MOD =(int)1e9+7;
// const int mod =(int)998244353;
const int mod =(int)1e9+7;

const int MAX =510000;
ll fac[MAX],finv[MAX],inv[MAX];
void COMint(){
    fac[0]=fac[1]=1;
    finv[0]=finv[1]=1;
    inv[1]=1;
    for(int i=2;i<MAX;i++){
        fac[i]=fac[i-1]*i%MOD;
        inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;
        finv[i]=finv[i-1]*inv[i]%MOD;
    }
}
ll COM(int n,int k){
    if(n<k) return 0;
    if(n<0||k<0)return 0;
    return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD;
}
ll gcd(ll a,ll b){
    if(a<0)a=-a;
    if(b<0)b=-b;
    if(b==0)return a;
    if(a>b){
        swap(a,b);
    }
    return gcd(a,b%a);
}
ll lcm(ll a,ll b){
  if(a<0)a=-a;
  if(b<0)b=-b;
    ll g;g=gcd(a,b);
    return b/g*a;
}
bool compare_by_b(pair<int, int> a, pair<int, int> b) {
    if(a.second != b.second){
        return a.second < b.second;
    }else{
        return a.first < b.first;
    }
}
bool compare_by_a(pair<int, int> a, pair<int, int> b) {
    if(a.first != b.first){
        return a.first < b.first;
    }else{
        return a.second < b.second;
    }
}
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
ll RS(ll N,ll P){
    if(P==0){
        return 1;
    }else{
        if(P%2==0){
            ll t=RS(N,P/2);
            return t*t;
        }else{
            return N*RS(N,P-1);
        }
    }
}
 struct UnionFind{
     vi d;
     vi cntWhite;
     UnionFind(int n):d(n,-1),cntWhite(n,0){};
     int deb(int x){
         return d[x];
     }
     int root(int x){
         if(d[x]<0)return x;
         return d[x]=root(d[x]);
     }
     int unite(int x,int y){
         x=root(x);y=root(y);
         if(d[x]>d[y])swap(x,y);
         d[x]+=d[y];
         cntWhite[x]+=cntWhite[y];
         d[y]=x;
         return true;
     }
     bool same(int x,int y){return root(x)==root(y);}
     int size(int x){return -d[root(x)];}
 };
int main() {
  ios::sync_with_stdio(false);
  int N=in();
  map<int,int>m;
  m[0]=1;
  REP(i, N){
      int d=in();
      m[d]++;
  }
  vector<int>ans;
  //同じdに3人以上いると必ず2人は同じ時刻になる。
  int p=1;
  for(auto i=m.begin();i!=m.end();i++){
    int a=i->first;
    int b=i->second;
    if(b>=3){
        cout<<0<<endl;
        return 0;
    }
    if(b==2&&a==12){
        cout<<0<<endl;
        return 0;
    }
    if(b==2){
        ans.pb(-a);
        ans.pb(a);
    }
    if(b==1){
        ans.pb(p*a);
        p*=-1;
    }
  }
  sort(all(ans));
  int final_ans=INF;
  REP(i,ans.size()-1){
      final_ans=min(final_ans,ans[i+1]-ans[i]);
  }
  final_ans=min(final_ans,ans[0]-ans[ans.size()-1]+24);
  cout<<final_ans<<endl;

  
  
  return 0;
} 


Measured memory_bytes: 3636