/in/foo.cc: In function 'int main()':
/in/foo.cc:27:29: warning: array subscript has type 'char' [-Wchar-subscripts]
         if(isalpha(ch)) a[ch]++;
                             ^
/in/foo.cc:35:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<p.size();i++) {
                 ~^~~~~~~~~
/in/foo.cc:33:8: warning: 'e' may be used uninitialized in this function [-Wmaybe-uninitialized]
     n=e-'e';
       ~^~~~