foo.cc: In function 'int Length(char*)':
foo.cc:6:16: error: 'strlen' was not declared in this scope
    6 |         return 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;

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