foo.cc: In function 'int main()':
foo.cc:8:14: 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(i=0;i<s.length();i++)
      |             ~^~~~~~~~~~~
foo.cc:5:9: warning: unused variable 'n' [-Wunused-variable]
    5 |     int n,x,i,sum=0;
      |         ^
foo.cc:5:11: warning: unused variable 'x' [-Wunused-variable]
    5 |     int n,x,i,sum=0;
      |           ^

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