t = int(input().strip())

for _ in range(t):
    n = int(input().strip())
    city = []
    for __ in range(n):
        city.append( ['.']*n )
    city[n-1][n-2] = 'C'    
    city[n-2][n-1] = 'C'
    
    for row in city:
        print( ''.join(row) )