P = int(input())
A = int(input())
TA = []
for _ in range(A):
    AK,AV = map(int,input().split())
    TA.append([AK,AV])
E = int(input())
TE = []
for _ in range(E):
    EK,EV = map(int,input().split())
    TE.append([EK,EV])
Kozos = []
kezdet = 0
for i in range(A):
    a = TA[i][0]
    b = TA[i][1]
    for j in range(kezdet,E):
        c = TE[j][0]
        d = TE[j][1]
        if a >= c and b <= d:
            Kozos.append([a,b])
        elif c >= a and d <= b:
            Kozos.append([c,d])
        elif a < c and c < b <= d:
            Kozos.append([c,b])
        elif c < a < d and b >= d:
            Kozos.append([a,d])
        elif c < a and a < d <= b:
            Kozos.append([a,d])
        elif a < c < b and d >= b:
            Kozos.append([c,b])
        if d <= b:
            kezdet = j
        if c >= b:
            break
print(len(Kozos))
for k in Kozos:
    print(*k)