# 根本不用動態規劃

N,M=map(int,input().split())
L=[]
for i in range(N+M):
    L.append([int(x) for x in input().split()])
L=sorted(L, key=lambda x:x[0]-x[1])[::-1]
S=0
i=0
while i<M:
    S+=L[i][1]
    i+=1
while i<M+N:
    S+=L[i][0]
    i+=1
print(S)