Finding multiple matches

Two new data.tables have been loaded in your workspace:

life_exp: contains the life expectancy of each country in 2010 sourced from the Gapminder foundation
continents: contains a mapping between each country and the continent(s) they are part of built from information provided by Countries-ofthe-World.com.

In this exercise, you will find the countries that are listed in more than one continent

XP

Complete the code to build a data.table containing the number of matches in continents for each row in life_exp.