from itertools import product
from bisect import bisect_right as br

n=int(input())
ss=[input() for i in range(n)]
ans=10

for p in product([0,1],repeat=(n*(n-1)//2)):
    shori=[0]*n
    pind=0
    for i in range(n-1):
        for j in range(i+1,n):
            if ss[i][j] == 'o':
                shori[i] += 1
            elif ss[i][j] == 'x':
                shori[j] += 1
            else:
                if p[pind] == 1:
                    shori[i] += 1
                else:
                    shori[j] += 1
            pind += 1
            
    shori_s=sorted(list(set(shori)))
    ans = min(ans , len(set(shori))-br(shori_s,shori[0])+1 )
    
print(ans)