/in/foo.cc: In function 'int main()':
/in/foo.cc:7:8: error: 'cin' was not declared in this scope
  while(cin>>n){
        ^
/in/foo.cc:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for(int k = 0;k < s[j].size();k++){
                      ^
/in/foo.cc:34:28: error: 'cout' was not declared in this scope
   for(int i = 0;i < n;i++) cout<<s[i]<<endl;
                            ^
/in/foo.cc:34:40: error: 'endl' was not declared in this scope
   for(int i = 0;i < n;i++) cout<<s[i]<<endl;
                                        ^