乐乐想写一个程序，避免自己不停地做重复事情。
只要你给程序一串字符串 他就能把字符串打印20次。
例如输入："abc"字符串，程序就把abc重复20次，得到下面的超长字符串
"abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc"
一个字符串
把输入的字符串重复20次
abc
abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
