foo.cc: In function ‘int main()’:
foo.cc:7:22: 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=1;i<n.size();i++)
      |                     ~^~~~~~~~~
foo.cc:9:23: error: ‘s’ was not declared in this scope
    9 |                 cout<<s[i];
      |                       ^
foo.cc:11:15: error: ‘s’ was not declared in this scope
   11 |         cout<<s[0];
      |               ^