Bolygók

from sys import stdin, stdout
def main():
    line1 = stdin.readline().strip().split()
    a = int(line1[0])  # Az első elem eltárolása
    b = int(line1[1])  # A második elem eltárolása
    lista1 = []
    for i in range(a):
        line = stdin.readline().strip().split()
        lista1.append([int(line[0]), int(line[1])])
    lista2 = []
    for i in range(b):
        line = stdin.readline().strip().split()
        lista2.append([int(line[0]), int(line[1])])
    if lista1[-1][1] > lista2[-1][1]:
        evek =  lista1[-1][1]
    else:
        evek = lista2[-1][1]
    evek1 = [0] * evek
    evek2 = [0] * evek
    for interval in lista1:
        for i in range(interval[0]-1, interval[1]):
            evek1[i] = 1
    for interval in lista2:
        for i in range(interval[0]-1, interval[1]):
            evek2[i] = 1
    intervals = []
    db = 0
    start = None
    for i in range(len(evek1)):
        if evek1[i] != evek2[i]:
            if start is None:
                start = i
                db += 1
        else:
            if start is not None:
                intervals.append((start+1, i))
                start = None
    if start is not None:
        intervals.append((start+1, len(evek1)))
    stdout.write(str(db) + '\n')
    for i in intervals:
        stdout.write(str(i[0]) + ' ' + str(i[1]) + '\n')
main()