666 B | 666 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def f(s):
return len(set(list(s.replace(" ", ""))))
def solve():
n = ii()
ans = input()
mx = f(ans)
for _ in range(n - 1):
s = input()
crt = f(s)
if mx < crt:
mx = crt
ans = s
elif mx == crt:
if ans > s:
ans = s
return ans
if __name__ == "__main__":
tc = ii()
for t in range(1, tc+1):
ret = solve()
p(f"Case #{t}: {ret}")