foo.cc: In function 'int main()':
foo.cc:14:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |         for(int i=0;i<s1.length();i++)
      |                     ~^~~~~~~~~~~~
foo.cc:27:37: error: 'strlen' was not declared in this scope
   27 |                                 i=i+strlen(s4)-1;
      |                                     ^~~~~~
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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