n = int(input())
m = []
for i in range(n):
m.append(input())
l = m[0][0]
other = m[0][1]
for i in range((n//2)):
if m[i][i] != l or m[i][n-1-i] != l or m[n-1-i][i] != l or m[n-1-i][n-1-i] != l:
print("NO")
exit()
if m[((n+1)//2)-1][((n+1)//2)-1] == l and m[((n+1)//2)-1].count(l) == 1:
for i in range(n):
for j in range(n):
if m[i].count(l) > 2 or m[i][j] != other and m[i][j] != l or len(set(m[i])) == 1:
print("NO")
exit()
print("YES")
exit()
print("NO")
#include <bits/stdc++.h>
#define fi first
#define se second
#define ll long long
using namespace std;
long long w1,w2,w3,n,k,l,i,j,a,mn,x,b,mx,ans,sum,s5,s1,s2,s3,s4,ch1,ch2,r,so,flag,g,num,f;
pair < ll,ll > pr[100001],rp[100001];
string sd[400],sf,m1,m2,sg;
stringstream ss;
char c1,c2,c3,c4,c;
int main()
{
mx=1e9;
// freopen("input.txt","r",stdin);
// freopen("output.txt","w",stdout);
cin >> n;
for(i=0;i<n;i++)
{
cin >> sd[i];
}
c1=sd[0][0];
c2=sd[0][1];
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if(sd[i][j]==c1)
{
s1++;
}
}
if(s1>2 or (i==n/2 and s1>=2))
{
cout << "NO" << endl;
return 0;
}
s1=0;
if(sd[i][i]!=c1 or sd[i][i+1]==c1)
{
cout << "NO" << endl;
return 0;
}
if(sd[i][n-i-1]!=c1 or sd[i][n-i-2]==c1)
{
cout << "NO" << endl;
return 0;
}
}
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if(sd[i][j]!=c1 and sd[i][j]!=c2)
{
cout << "NO" << endl;
return 0;
}
}
}
cout << "YES" << endl;
return 0;
}
/*
48
57
*/
1327B - Princesses and Princes | 1450F - The Struggling Contestant |
1399B - Gifts Fixing | 1138A - Sushi for Two |
982C - Cut 'em all | 931A - Friends Meeting |
1594A - Consecutive Sum Riddle | 1466A - Bovine Dilemma |
454A - Little Pony and Crystal Mine | 2A - Winner |
1622B - Berland Music | 1139B - Chocolates |
1371A - Magical Sticks | 1253A - Single Push |
706B - Interesting drink | 1265A - Beautiful String |
214A - System of Equations | 287A - IQ Test |
1108A - Two distinct points | 1064A - Make a triangle |
1245C - Constanze's Machine | 1005A - Tanya and Stairways |
1663F - In Every Generation | 1108B - Divisors of Two Integers |
1175A - From Hero to Zero | 1141A - Game 23 |
1401B - Ternary Sequence | 598A - Tricky Sum |
519A - A and B and Chess | 725B - Food on the Plane |