foo.cc: In function 'int zuida(std::string, int)':
foo.cc:8:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    8 |  for(int i=0;i<a.length();i++)
      |              ~^~~~~~~~~~~
foo.cc:10:9: warning: array subscript has type 'char' [-Wchar-subscripts]
   10 |   m[a[i]]++;
      |         ^
foo.cc:12:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |  for(int i=0;i<a.length();i++)
      |              ~^~~~~~~~~~~
foo.cc:14:12: warning: array subscript has type 'char' [-Wchar-subscripts]
   14 |   if(m[a[i]]>=k)
      |            ^

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