s = list(map(int, input().split()))
m = min(s)
def check(mid):
    stn = 0
    for i in s:
        if(i>mid):
            stn += int((i-mid)/2)
    return m+stn>=mid
left = m
right = max(s)
ans = left
while(left<=right):
    mid = int((left+right)/2)
    if(check(mid)):
        ans = mid
        left = mid+1
    else:
        right = mid-1

print(ans)