num=int(input())
time=int(input())
biao=[]
for i in range(num):
    hhh=list(map(int,input().split()))
    biao.append(hhh)
res=[]
for i in range(num):
    if biao[i][1]<=time<=biao[i][2]:
        res.append(biao[i][0])
if len(res)==0:
    print('null')
else:
    res=sorted(res)
    for i in res:
        print(i)