foo.cc: In function 'int main(int, const char**)':
foo.cc:55:13: error: 'strlen' was not declared in this scope
   55 |  int length=strlen(s);
      |             ^~~~~~
foo.cc:3:1: note: 'strlen' is defined in header '<cstring>'; did you forget to '#include <cstring>'?
    2 | #include <iostream>
  +++ |+#include <cstring>
    3 | using namespace std;

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