#include <bits/stdc++.h>
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define REP(i,k,n) for(ll i=k;i<(ll)(n);i++)
#define fore(i,a) for(auto &i:a)
using namespace std;
using ll = long long; 

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