with open('02a.txt') as f:
    text = f.read().strip()

def make_report(line):
    return [int(x.strip()) for x in line.split()]

reports = [make_report(x) for x in text.split('\n')]

def test_report(report):
    if len(report) == 1:
        return True
    dir = 1 if report[1] - report[0] > 0 else -1
    for i in range(len(report)-1):
        diff = (report[i+1] - report[i]) * dir
        if diff < 1 or diff > 3:
            return False
    return True

def test_sub_reports(report):
    for i in range(len(report)):
        if test_report(report[:i] + report[i+1:]):
            return True
    return False

print(sum(test_sub_reports(x) for x in reports))