foo.cc: In function 'int countChar(std::string, char)':
foo.cc:8:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    8 |  for(int i=0;i<s.size();i++)
      |              ~^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:18:6: warning: unused variable 't' [-Wunused-variable]
   18 |  int t,i,n,len,rk;
      |      ^

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