In CODE FESTIVAL XXXX, there are N+1 participants from all over the world, including Takahashi.

Takahashi checked and found that the time gap (defined below) between the local times in his city and the i-th person's city was D_i hours. The time gap between two cities is defined as follows. For two cities A and B, if the local time in city B is d o'clock at the moment when the local time in city A is 0 o'clock, then the time gap between these two cities is defined to be min(d,24-d) hours. Here, we are using 24-hour notation. That is, the local time in the i-th person's city is either d o'clock or 24-d o'clock at the moment when the local time in Takahashi's city is 0 o'clock, for example.

Then, for each pair of two people chosen from the N+1 people, he wrote out the time gap between their cities. Let the smallest time gap among them be s hours.

Find the maximum possible value of s.

Constraints

* 1 \leq N \leq 50
* 0 \leq D_i \leq 12
* All input values are integers.

Input

Input is given from Standard Input in the following format:


N
D_1 D_2 ... D_N


Output

Print the maximum possible value of s.

Examples

Input

3
7 12 8


Output

4


Input

2
11 11


Output

2


Input

1
0


Output

0
#include <stdio.h>
int max(int a,int b){
    if(a>b)return a;
    return b;
}
int min(int a,int b){
    if(a>b)return b;
    return a;
}
int abs(int a){
    if(a>0)return a;
    return -a;
}
int d(int a,int b){
    return min(abs(a-b)%24,abs(24-abs(a-b))%24);
}
bool check(bool a[],int ans){
    bool temp[24];
    for(int i=0;i<24;i++)temp[i]=a[i];
    for(int i=0;i<24;i++)if(temp[i])for(int j=i+1;j<24;j++)if(temp[j]){
        if(d(i,j)<ans){
            if(j>=12)return false;
            temp[j]=false;
            temp[24-j]=true;
        }
    }
    return true;
}
int main(){
    int n,temp;
    bool a[25];
    scanf("%d",&n);
    for(int i=0;i<24;i++)a[i]=false;
    a[0]=a[24]=true;
    for(int i=0;i<n;i++){
        scanf("%d",&temp);
        if(a[temp]){
            if(a[24-temp]){
                printf("0\n");
                return 0;
            }
            a[24-temp]=true;
        }
        else a[temp]=true;
    }
    for(int i=23;i>0;i--){
        if(check(a,i)){
            printf("%d\n",i);
            return 0;
        }
    }
}