from sys import stdin
def main():
    #入力
    readline=stdin.readline
    n,k=map(int,readline().split())

    if n%2==0:
        if k>=n//2:
            print(n//2)
        else:
            print(k+1)

    else:
        print(min(n,k+1))
if __name__=="__main__":
    main()