/in/foo.cc: In function 'int main()':
/in/foo.cc:9:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int i = 0;i < k.length();i++){
               ~~^~~~~~~~~~~~
/in/foo.cc:5:5: warning: variable 'n' set but not used [-Wunused-but-set-variable]
 int n;
     ^