/in/foo.cc: In function 'int main()':
/in/foo.cc:17:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i==0&&s2[i]==','||i==s2.size()-1&&s2[i]==',')
                        ~^~~~~~~~~~~~~
/in/foo.cc:17:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(i==0&&s2[i]==','||i==s2.size()-1&&s2[i]==',')
      ~~~~^~~~~~~~~~~~