N = int(input())
S = [input() for _ in range(N)]
W0 = [0] * N
G = []
for i in range(N - 1):
    for j in range(i + 1, N):
        if S[i][j] == "o":
            W0[i] += 1
        elif S[i][j] == "x":
            W0[j] += 1
        else:
            G.append((i, j))
NG = len(G)
ans = 6
for i in range(1 << NG):
    W = W0[:]
    for j in range(NG):
        if i & (1 << j):
            W[G[j][0]] += 1
        else:
            W[G[j][1]] += 1
    w0 = W[0]
    cnt = 1
    for k in range(6, w0, -1):
        if k in W:
            cnt += 1
    ans = min(ans, cnt)
print(ans)