foo.cc: In function 'int main()':
foo.cc:12:2: error: 'vector' was not declared in this scope
  vector<string> v;
  ^~~~~~
foo.cc:12:2: note: suggested alternative: 'qecvt_r'
  vector<string> v;
  ^~~~~~
  qecvt_r
foo.cc:12:15: error: expected primary-expression before '>' token
  vector<string> v;
               ^
foo.cc:12:17: error: 'v' was not declared in this scope
  vector<string> v;
                 ^
foo.cc:20:11: warning: array subscript has type 'char' [-Wchar-subscripts]
   cnt[s[0]]++;
           ^
foo.cc:27:14: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
   if(cnt[i]&1==1) sig=i;
             ~^~~

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