#include<bits/stdc++.h>
int read(){
	char c=getchar();while (c!='-'&&(c<'0'||c>'9'))c=getchar();
	int k=1,kk=0;if (c=='-')c=getchar(),k=-1;
	while (c>='0'&&c<='9')kk=kk*10+c-'0',c=getchar();return k*kk;
}using namespace std;
int n,mi,a[1000],ff,f[1000];
bool pd(int x){
	for (int i=1;i<=n;i++){
		ff=0;f[i]=a[i];
		for (int j=0;j<i;j++)
			if (min(max(f[i],f[j])-min(f[i],f[j]),min(f[i],f[j])-max(f[i],f[j])+24)<x)ff=1;
		if (ff)ff=0,f[i]=24-a[i];
		for (int j=0;j<i;j++)
			if (min(max(f[i],f[j])-min(f[i],f[j]),min(f[i],f[j])-max(f[i],f[j])+24)<x)ff=1;
		if (ff)return 0;
	}return 1;
}
int main(){
	n=read();mi=100;
	for (int i=1;i<=n;i++)a[i]=read();sort(a+1,a+1+n);
	for (int i=a[1];i>=0;i--)
		if (pd(i)){cout<<i<<endl;return 0;}
}
