/in/foo.cc: In function 'int main()':
/in/foo.cc:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<=n.length()-1;i++)
                 ~^~~~~~~~~~~~~~
/in/foo.cc:7:10: warning: unused variable 'flag' [-Wunused-variable]
     bool flag=0;
          ^~~~
/in/foo.cc:9:9: warning: unused variable 'lenn' [-Wunused-variable]
     int lenn=n.length();
         ^~~~