#!/usr/bin/python
import sys,re

n,m=map(int,raw_input().split())
assert 1 <= n <= 1000
assert 1 <= m <= 1000
b,r=map(int,raw_input().split())
assert 1 <= b <= 10**9
assert 0 <= r <= 10**6
event=[map(int,raw_input().split()) for k in range(r)]
group = []
for i in range(len(event)):
    si, ki, ti = event[i]
    assert 0 <= si < b
    assert 1 <= ki <= n
    assert 0 <= ti <= m
    if i > 0:
        assert event[i-1][0] <= event[i][0]
    if not (group and group[-1][0] == si):
        group += [(si, [])]
    group[-1][1].append((ki, ti))

k2t = [0] * (n+1)
owner = [0] * (m+1)
for si, log in group:
    kids = map(lambda x:x[0], log)
    assert len(kids) == len(set(kids)), \
            "@%d: at least one kid switched toy more than once in one time unit" % si
    for ki, ti in log:
        if ti > 0:
            assert k2t[ki] != ti, \
                "@%d: kid %d is switching from toy %d to the same toy" % (si, ki, ti)
    for ki, ti in log:
        owner[k2t[ki]] = 0
    for ki, ti in log:
        if ti > 0:
            assert owner[ti] == 0, \
                "@%d: kid %d is switching to toy %d but it is already held by kid %d" % (si, ki, ti, owner[ti])
        owner[ti] = ki
        k2t[ki] = ti


# Nothing to report.
sys.exit(42)