#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

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