struct MovedCargo { uint moved = 0, remainder = 0; };

/* 1: */
 used_stations.emplace_back(std::make_pair(st, MovedCargo()));

/* 2: */
 used_stations.emplace_back(std::make_pair(st, MovedCargo{}));

/* 3: */
 MovedCargo zero;
 used_stations.emplace_back(std::make_pair(st, zero));