def is_safe(report):
    increasing = report[1] > report[0]
    decreasing = report[1] < report[0]

    for i in range(1, len(report)):
        diff = report[i] - report[i - 1]
        abs_diff = abs(diff)
        if abs_diff < 1 or abs_diff > 3:
            return False
        if (diff > 0 and not increasing) or (diff < 0 and not decreasing):
            return False

    return True

def is_safe_with_dampener(report):
    if is_safe(report):
        return True
    for i in range(len(report)):
        modified_report = report[:i] + report[i+1:]
        if is_safe(modified_report):
            return True

    return False

def read_reports_from_file(filename):
    reports = []
    with open(filename, 'r') as file:
        for line in file:
            report = list(map(int, line.split()))
            reports.append(report)
    return reports

def main():
    filename = 'input.txt' 
    reports = read_reports_from_file(filename)

    safe_count = 0
    for report in reports:
        if is_safe_with_dampener(report):
            safe_count += 1

    print("OUTPUT:", safe_count)

if __name__ == "__main__":
    main()