//#define _GLIBCXX_DEBUG
#include<bits/stdc++.h>
#define PI 3.14159265359
using namespace std;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define bit(n,k) (((ll)n>>(ll)k)&1) /*nのk bit目*/
const long long INF= 1e+18+1;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll> >vvl;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> T;
//const ll MOD=1000000007LL;
const ll MOD=998244353LL;
string abc="abcdefghijklmnopqrstuvwxyz";
string ABC="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
vl dx={-1,-1,-1,0,0,1,1,1};
vl dy={1,-1,0,1,-1,1,0,-1};

int main(){
  ll n,k;cin>>n>>k;
  if(n%2==0){
    if(k>=n/2){
      cout<<n/2<<endl;
    }
    else {
      cout<<k+1<<endl;
    }
  }
  else {
    if(k%2==1){
      cout<<min(n-1,k+1)/2+min(n,k)/2+1<<endl;
    }
    else {
      cout<<min(n,k+1)/2+1+min(n-1,k)/2<<endl;
    }

  }
}