#include using namespace std; #define REP(i,n) for(int i=0; i #define VLL vector #define VVI vector> #define VVLL vector> #define VC vector #define VS vector #define VVC vector> #define fore(i,a) for(auto &i:a) typedef long long ll; typedef pair P; template bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } template bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } const int INF = 2147483647; const ll INFL = 9223372036854775807; const ll mod = 1000000007; int main() { int l, k; cin >> l >> k; cout << (l - 1) / (2 * k)*k << endl; return 0; }