# coding: utf-8

N, K = map(int,input().split())


if N % 2 == 0:
    if K+1 >= N//2:#1周してるか
        ans = N//2
    else:
        ans = K+1
else:
    if K+1 >= N:
        ans = N
    else:
        ans = K+1

print(ans)