LOS ANGELES -- Iron Man 3 is the heavy-lifter at theaters with a colossal overseas debut that overshadows a sleepy presummer weekend at the domestic box office.The superhero sequel starring Robert Downey Jr. got a head-start on its domestic launch next Friday with a $195.3 million opening in 42 overseas markets. Sunday studio estimates show director Michael Bay's true-crime tale Pain & Gain muscled into first-place domestically with a $20 million debut. The movie starring Mark Wahlberg, Dwayne Johnson and Anthony Mackie knocked off Tom Cruise's sci-fi adventure Oblivion after a week in the No. 1 spot. Oblivion slipped to second-place with $17.4 million, raising its domestic total to $64.7 million.