def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    
    N = int(data[0])
    M = int(data[1])
    grid = data[2:2+N]
    
    count = 0
    for row in grid:
        count += row.count('.')
    
    if count % 2 != 0:
        print("NO")
    else:
        print("YES")

if __name__ == '__main__':
    main()