/in/foo.cc: In function 'int main()':
/in/foo.cc:7:24: error: 'strlen' was not declared in this scope
    7 |         for(int i=0; i<strlen(s); i++)
      |                        ^~~~~~
/in/foo.cc:3:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    2 | #include <iomanip>
  +++ |+#include <cstring>
    3 | using namespace std;