int ret = 0;
if (canKill(position, rposition) && canKill(rposition, position)) throw new Error();
if (canKill(position, rposition)) ret = -1;
int ret = 0;
if (canKill(position, rposition) && canKill(rposition, position)) throw new Error();
if (canKill(position, rposition)) ret = -1;