from math import *
def max(x,y):
    if x>y:
        return x
    return y
def min(x,y):
    if x<y:
        return x
    return y

count=0
words = list(map(int, input().strip().split()))
if (words[0]<3 or words[1]<3):
    print(count)
else:
    print(floor((words[0]+words[1])/3))