covering_segments

# Uses python3
import sys
from collections import namedtuple

Segment = namedtuple('Segment', 'start end')


def optimal_points(segments):
    points = []
    # we first sort segments by increasing right end point order
    segments.sort(key=lambda segment: segment[1])
    i = 0
    while i <= len(segments) - 1:
        # a safe move is to add the first right end point of the minimum segment to the list
        end_point = segments[i].end
        points.append(end_point)
        i += 1
        # we look for the next segment whose start point is not covered by the current end point
        while i <= len(segments) - 1 and end_point >= segments[i].start:
            i += 1
    return points


if __name__ == '__main__':
    user_input = sys.stdin.read()
    n, *data = map(int, user_input.split())
    segments = list(map(lambda x: Segment(x[0], x[1]), zip(data[::2], data[1::2])))
    points = optimal_points(segments)
    print(len(points))
    for p in points:
        print(p, end=' ')