foo.cc: In function 'int main()':
foo.cc:12:18: error: 'strlen' was not declared in this scope
   12 |         if (a <= strlen(s))
      |                  ^~~~~~
foo.cc:3:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    2 | #include <string>
  +++ |+#include <cstring>
    3 | using namespace std;

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