def inp(): # For taking integer inputs.
    return(int(input()))

def inlst(): # For taking List inputs.
    return(list(map(int,input().split())))

# For taking string inputs. Actually it returns a List of Characters, instead of a string, 
def instr():
    s = input()
    return(list(s[:len(s)]))

n = inp()
board = ["" for _ in range(n)]
for i in range(n):
    board[i] = instr()

def checkRow(row):
    b = 0
    w = 0
    wThre = 0
    bThre = 0
    for c in row:
        if c == "W":
            w += 1
            wThre += 1
            bThre = 0
        else:
            b += 1
            wThre = 0
            bThre += 1
        if bThre == 3 or wThre == 3:
            # print("YAY")
            return False
    return w==b

def checkCol(i):
    b = 0
    w = 0
    wThre = 0
    bThre = 0
    for j in range(len(board)):
        if board[j][i] == "W":
            w += 1
            wThre += 1
            bThre = 0
        else:
            b += 1
            wThre = 0
            bThre += 1
        if bThre == 3 or wThre == 3:
            # print("NAY")
            return False
            
    
    return w==b

valid = True
for i in range(len(board[0])):
    valid = checkCol(i)
    # print(valid)
    if not valid:
        
        print(0)
        break
if valid:
    for row in board:
        # print(row)
        valid = checkRow(row)
        # print(valid)
        if not valid:
            print(0)
            break
if valid:
    print(1)