#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  ll N,K;
  cin>>N>>K;

  if(N%2==0){
    int ans=min(N/2,K/2+(K-1)/2+2);
    cout<<ans<<endl;
    return 0;
  }else{
    int ans=min(N,K/2+(K-1)/2+2);
    cout<<ans<<endl;
  }

  return 0;
}