#include #include using namespace std; using namespace atcoder; typedef long long int ll; typedef long double ld; #define FOR(i,l,r) for(ll i=l;i=l;i--) #define RREP(i,n) RFOR(i,0,n) #define ALL(x) x.begin(),x.end() #define P pair #define F first #define S second #define BS(A,x) binary_search(ALL(A),x) #define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin()) #define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin()) #define COU(A,x) UB(A,x)-LB(A,x) templateusing min_priority_queue=priority_queue,greater>; using mint=modint1000000007; signed main(){ ll L,K;cin>>L>>K;cout<<(L-1)/(2*K)*K<