foo.cc: In function 'int main()':
foo.cc:36:27: warning: array subscript has type 'char' [-Wchar-subscripts]
   36 |         if(isalpha(ch)) a[ch]++;
      |                           ^~
foo.cc:47:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |     for(int i=0;i<p.size();i++)
      |                 ~^~~~~~~~~
foo.cc:43:8: warning: 'e' may be used uninitialized in this function [-Wmaybe-uninitialized]
   43 |     n=e-'e';
      |       ~^~~~

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