#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import array
from bisect import *
from collections import *
import fractions
import heapq
from itertools import *
import math
import random
import re
import string
import sys

def solve_slow(N, K):
    cur = set([1])
    for k in range(K):
        next_cur = set()
        for c in cur:
            c1 = c + 1
            if c1 == N + 1: c1 = 1
            c2 = c - 1
            if c2 == 0: c2 = N
            next_cur.update([c1, c2])
        cur = next_cur
        # print(cur)
    return len(cur)

def solve(N, K):
    if N % 2 == 1:
        return min(K + 1, N)
    else:
        return min(K + 1, N // 2)

# for n in range(1, 10):
#     for k in range(1, 20):
#         gt = solve_slow(n, k)
#         mine = solve(n, k)
#         if gt != mine:
#             print("error")
#             pritn(n, k, gt, mine)

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