foo.cc: In function 'int main()':
foo.cc:8:10: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    8 | for(i=0;i<s.size();i++)
      |         ~^~~~~~~~~
foo.cc:11:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   11 |  if(n>=65&&n<=90||n>=97&&n<=122)
      |     ~~~~~^~~~~~~

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