Crowds stretched the length of Avenue des Champs-Elysees in Paris on Saturday, as Pope Leo urged Catholics to find happiness in faith, not material things, at the biggest event of his visit to France, an outdoor Mass with an estimated 800,000 people.Chants of "Leo, Leo" and "Long live the Pope" echoed down the roughly 2 km tree-lined boulevard, from Place de la Concorde to Arc de Triomphe, as people pressed against security barriers for a glimpse of Leo as he arrived in a popemobile.Attendees included Brigitte Macron, the French president's wife, far-right leader Marine Le Pen, who is leading in the polls ahead of next year's presidential election, Prime Minister Sebastien Lecornu and Bernard Arnault, the billionaire chairman of French luxury group LVMH.Cheers rang out in the crowd as Leo thanked God in his sermon for the chance to visit France on a whirlwind four-day, three-city tour, during which he is seeking to repair the Church's standing after abuse scandals caused nationwide shock. The pope told Catholics that only their faith would provide true happiness. "Only God can fill the emptiness within us,"he said.