tests = int(input())

for case in range(1, tests+1):
    n = int(input())

    # binary search on 26 * (1+2+3+...k) = 26 * (k+1)*k/2
    lo = 0
    hi = pow(10, 7)
    # invariant: [lo, hi] is the smallest value with 26*(k+1)*k/2 > n
    while hi - lo >= 1:
        mid = (hi + lo) // 2
        val = 13 * (mid+1) * mid
        if val >= n:
            hi = mid
        else:
            lo = mid + 1
    # lo is the sequence we want, where nth character resides.
    subtract = 13 * (lo) * (lo-1)
    n -= subtract
    i = lo
    ind = (n-1) // i
    character = chr(ord('a') + ind)
    print(f"Case #{case}: {character.upper()}")