foo.cc: In function 'int main()':
foo.cc:7:17: error: 'strlen' was not declared in this scope
    7 |         int n = strlen(a);
      |                 ^~~~~~
foo.cc:2:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    1 | #include <stdio.h>
  +++ |+#include <cstring>
    2 | int main()

[Hydro](https://hydro.ac)提供评测服务