def solution():
    N = int(input().strip())
    cnt = (N-1)//26
    x = int((-1+(1+8*cnt)**0.5)/2)
    while ((x+1)+1)*(x+1) <= 2*cnt:
        x += 1
    return chr(ord('A')+(N-26*(x+1)*x//2-1)//(x+1))

for case in range(int(input())):
    print('Case #%d: %s' % (case+1, solution()))