def getMin(S,c):
    ret = 99
    N = len(S)
    if c <= 0:
        rank = [0 for i in range(N)]
        v = S[0].count('o')
        for i in range(N):
            rank[S[i].count('o')] += 1
        r = 1
        for i in range(N - 1,-1,-1):
            if rank[i] == 0:continue
            if i == v:
                break
            r += 1
        ret = r
    else:
        used = [[False for j in range(N)]for i in range(N)]
        for i in range(N):
            for j in range(N):
                if i == j:continue
                if used[i][j]:continue
                if used[j][i]:continue
                if S[i][j] == '-':
                    S[i][j] = 'o'
                    S[j][i] = 'x'
                    ret = min(ret,getMin(S,c - 1))
                    S[i][j] = 'x'
                    S[j][i] = 'o'
                    ret = min(ret,getMin(S,c - 1))
                    S[i][j] = '-'
                    S[j][j] = '-'
                    used[i][j] = True
                    used[j][j] = True
    return ret
N = int(raw_input())
S = [list(raw_input()) for i in range(N)]
for i in range(1,N):
    if S[0][i] == '-':
        S[0][i] = 'o'
        S[i][0] = 'x'
c = sum([S[i].count('-') for i in range(1,N)]) / 2
print getMin(S,c)