设s、t 为两个字符串，两个字符串分为两行输出，判断t 是否为s 的子串。如果是，输出子串所在位置（第一个字符，字符串的起始位置从0开始），否则输出-1-Set s, t for two strings, two strings can be divided into two lines of output, judge whether t for s substring. If it is, output substring location (the first character of a string, starting position starting from 0), or output- 1