n = int(input())
edges = [input().strip() for _ in range(n - 1)]
R_in = [0] * n
R_out = [0] * n
B_in = [0] * n
B_out = [0] * n
for i in range(n - 1):
    row = edges[i]
    for j_idx, color in enumerate(row):
        j = i + 1 + j_idx
        if color == 'R':
            R_out[i] += 1
            R_in[j] += 1
        else:
            B_out[i] += 1
            B_in[j] += 1
t_mixed_x2 = 0
s_in_out = 0
for v in range(n):
    road_R = R_in[v] + R_out[v]
    road_B = B_in[v] + B_out[v]
    t_mixed_x2 += road_R * road_B
    s_in_out += R_in[v] * B_out[v] + B_in[v] * R_out[v]
if t_mixed_x2 // 2 == s_in_out:
    print("YES")
else:
    print("NO")