N,K=map(int,input().split())
if N%2==0:
    if K%2==0:
        print(min(N//2,(K//2)*2+1))
    else:
        print(min(N//2,(K//2)*2+2))
else:
    if K%2==0:
        print(min(N,(K//2)*2+1))
    else:
        print(min(N,(K//2)*2+2))