foo.cc: In function 'std::string ans(std::string, int)':
foo.cc:7:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |     for(int i=0;i<s.size();i++)
      |                 ~^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:13:10: error: 'ket' was not declared in this scope; did you mean 'key'?
   13 |     cin>>ket>>s;
      |          ^~~
      |          key

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