A - Valera and X.cpp

/*
RAJAT SINGH
VIT VELLORE
*/

#include<bits/stdc++.h>
using namespace std;
#define ll   long long 
//#define max 706000
#define gc getchar_unlocked
#define pc putchar_unlocked
//inline void get(int *p){register  int n=0,sign=1,a=gc();while(a<'0'||a>'9'){ if(a=='-'){sign=-1;a=gc();break;} a=gc();}while(a>='0' && a<='9'){n=(n<<1)+(n<<3)+a-'0';a=gc();}*p=n*sign;}
  
 
//inline void put(int n){char d[10];int i=0;if(n<0){pc('-');n=-n;}do{d[i++]=n%10+'0';n=n/10;}while(n);while(i)pc(d[--i]);pc('\n');}
#define     sc(a)  scanf("%d",&a) 
#define     p(a)  printf("%d\n",a) 
#define     l(i,a)  for(int i=0;i<a;i++)
#define     re(j,a,b)  for(int j=a;j<=b;j++)  
# define ll   long long 
#define modu 1000000007
ll  modular_pow(ll int  base, ll int  exponent)
{
    if(exponent==0)
    return 1;
    else if(exponent%2==0){
        ll int res=modular_pow(base,exponent/2);
        return (res*res );
        
        
    }
    else{
        return (modular_pow(base,exponent-1) * base);
        
    }
}
 
 
 
 int gcd(int a,int b){
    if(b==0)
    return a;//gcd
    else return gcd(b,a%b);
 }
 
bool chek(int x){
    return (x&&!(x&(x-1)));// power of 2
}
int onebits(int n){
    return __builtin_popcount(n);//count number od set bits in a number
 
}


ll max(ll x, ll y){
	if(x>=y) return x;
	else return y;
}

int main() {

	freopen("inp.txt","r",stdin);
//string s= "rajat";
int n;
cin>>n;
char a[n+2][n+2];
l(i,n){
	l(j,n)cin>>a[i][j];
}
set< char >v;
set< char >d;
l(i,n){

l(j,n){
    if(i==j)	
	v.insert(a[i][j]);
	else{
	if(i+j==n-1)	v.insert(a[i][j]);
	else d.insert(a[i][j]);}
	
}}
if(v.size()==1&& d.size()==1 && *d.begin()!=*v.begin()) puts("YES");
else{
	 puts("NO");
}
//cout<<v.size()<<d.size();
return  0;}