there small spaceship surround group enemy large spaceship the space twodimensional plane group enemy spaceship position way integer ycoordinate xcoordinate equal 100 second group position way integer ycoordinate xcoordinate equal 100each spaceship group simultaneously shoot laser shot infinite ray destroy spaceship touch small spaceship time the small spaceship able avoid laser shot want position location x0 necessarily integer ycoordinate ray shot destroy enemy spaceship possible find large number spaceship destroy way assume enemy spaceship can not avoid laser shot