import sys sys.setrecursionlimit(200005) int1 = lambda x: int(x)-1 p2D = lambda x: print(*x, sep="\n") def II(): return int(sys.stdin.buffer.readline()) def LI(): return list(map(int, sys.stdin.buffer.readline().split())) def LI1(): return list(map(int1, sys.stdin.buffer.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def BI(): return sys.stdin.buffer.readline().rstrip() def SI(): return sys.stdin.buffer.readline().rstrip().decode() # dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] # dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] dij = [(0, 1), (1, 0), (1, 1), (1, -1)] inf = 10**16 md = 998244353 # md = 10**9+7 n, k = LI() if n & 1: if k & 1: ans = min(k+1, n) else: ans = min(k, n) else: ans = min(n//2, k+1) print(ans)