#include using namespace std; template using min_priority_queue = priority_queue,greater>; template void printv(vector &v){ bool b = false; for(auto i : v){ if(b) cout << " "; else b = true; cout << i; } cout << endl; } int64_t rand64(){ int64_t l = rand(); int64_t r = rand(); return (l<<31)+r; } template bool chmin(T &a, const T& b) { if (a > b) { a = b; // aをbで更新 return true; } return false; } template bool chmax(T &a, const T& b) { if (a < b) { a = b; // aをbで更新 return true; } return false; } bool yn(bool b){ if(b) cout << "Yes" << endl; else cout << "No" << endl; return b; } bool debug; bool randomInput; bool debugOutput; int numOfTestCase; using ans_type = int; void input(){ if(numOfTestCase > 1){ } if(randomInput){ } else{ } return; } void output_input(){ ; } ans_type calc(){ int L, K; cin >> L >> K; int cnt = (L-1)/(2*K); cout << cnt*K << endl; return ans_type(); } ans_type calc_simple(){ return ans_type(); } void output(ans_type ans){ return; } int main(){ debug = 0; randomInput = 0; debugOutput = 0; numOfTestCase = 1; srand(time(NULL)); cout << fixed << setprecision(12); if(numOfTestCase == 0) cin >> numOfTestCase; if(debug){ for(int i = 0; i < numOfTestCase; i++){ if(debugOutput) cout << string(16, '-') << endl; input(); ans_type ans = calc(); ans_type ansSimple = calc_simple(); if(ans != ansSimple){ output_input(); output(ans); output(ansSimple); } } } else{ for(int i = 0; i < numOfTestCase; i++){ input(); output(calc()); } } return 0; }