foo.cc: In function 'int main()':
foo.cc:9:18: error: 'strlen' was not declared in this scope
    9 |         long n = strlen(s);
      |                  ^~~~~~
foo.cc:2:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    1 | #include<iostream>
  +++ |+#include <cstring>
    2 | using namespace std;

[Hydro](https://hydro.ac)提供评测服务