正则表达式匹配行，但获得此行的一部分

Question

Import complete
Summary:
4 XXX were created
0 XXX had bbb created
0 XXX had a ccc created
2 XXX had ddd created

，我需要下一行：4 XXX were created 但因此我只需要一个数字4

如何获得它？

谢谢！