from sys import stdin
from math import sqrt
input = stdin.readline

def solve(x):
    a = 2*x/26

    sol = max(int((sqrt((1+4*a)) - 1)/2) - 2,0)

    summ = (sol*(2*26 + (sol-1)*26))//2

    sol+=1

    while summ+sol*26<x:
        summ+=sol*26
        sol+=1
    
    x -= summ

    char = chr(ord('A') + (x-1)//sol)

    return char

    


    

for i in range(int(input())):
    n = int(input())

    
    print(f'Case #{i+1}: {solve(n)}')