It's lonely at the top. Who knows it better than mountaineers?They won't trade it for anything. Those hours at the summit, lungs straining but mission accomplished, are the gilded moments in a climber's career, trophies moulded in suffering and sacrifice. Arjun Vajpai (29) has had a few of those in his expeditions to Everest, Kanchenjunga, Lhotse, Makalu, Cho Oyu and Manaslu. He knows the feeling well.