The government flagged more than 1.6 million foreign visitors for overstaying their visas from 2013 to 2015, but deportation agents said they fell too low on President Obama’s list of priorities to bother targeting for removal, according to a watchdog report released Monday. U.S. Immigration and Customs Enforcement , the deportation agency, concluded that it would cost too much to pursue the overstays, the Government Accountability Office said.