import itertools
 
n = int(input())
 
pt = [0] * n
yet = []
 
for i in range(n-1):
    s = input()
    for j in range(i+1, n):
        if s[j] == 'o':
            pt[i] += 1
        elif s[j] == 'x':
            pt[j] += 1
        else:
            if i == 0:
                pt[0] += 1
            else:
                yet.append([i, j])
 
if pt[0] == n - 1:
    print(1)
    exit()
 
size = len(yet)
rank = n
 
combinations = itertools.product([True, False], repeat=size)
 
for combo in combinations:
    pt2 = [0] * n
    for i in range(n): pt2[i] += pt[i]
 
    for i in range(len(combo)):
        if combo[i]:
            pt2[yet[i][0]] += 1
        else:
            pt2[yet[i][1]] += 1
 
    set1 = set(pt2)
    r = 1
    for x in range(n-1, pt2[0], -1):
        if x in set1:
            r += 1
    if rank > r:
        rank = r
 
print(rank)