759 B | 759 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
BLANK = " "
inp = input
# inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n = ii()
tm = [0] * 1100
mn = 111111111111111
mx = 0
for i in range(n):
_, a, b = input().split()
a = int(a)
b = int(b)
for j in range(a, b):
tm[j] += 1
mn = min(mn, a)
mx = max(mx, b)
for i in range(mn, mx):
if tm[i] == 0:
continue
p(end=chr(64 + tm[i]))
p()
if __name__ == "__main__":
tc = ii()
for t in range(1, tc+1):
ret = solve()