import sys
sys.stdin.readline
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))
mod=10**9+7

def main():
    N,K=MI()
    ans=0
    if N%2==0:
        ans=min(K+1,N//2)
    else:
        ans=min(1+K,N)
        
    print(ans)


main()