1
n = int(input())
2
table = [input() for i in range(n)]
3
 
4
result = 'YES'
5
 
6
for i in range(n):
7
    for j in range(n):
8
        cnt = 0
9
        
10
        if i - 1 >= 0 and table[i - 1][j] == 'o':
11
            cnt += 1
12
        if i + 1 < n and table[i + 1][j] == 'o':
13
            cnt += 1
14
        if j - 1 >= 0 and table[i][j - 1] == 'o':
15
            cnt += 1
16
        if j + 1 < n and table[i][j + 1] == 'o':
17
            cnt += 1
18
            
19
        if cnt % 2 != 0:
20
            result = 'NO'
21
            
22
print(result)