/in/foo.cc: In function 'int main()':
/in/foo.cc:7:20: warning: array subscript has type 'char' [-Wchar-subscripts]
  while(cin>>ch)a[ch]++;
                    ^
/in/foo.cc:11:19: warning: array subscript has type 'char' [-Wchar-subscripts]
   while(l<'z'&&a[l]%2==0)l++;//包括0个 
                   ^
/in/foo.cc:12:19: warning: array subscript has type 'char' [-Wchar-subscripts]
   while(r>'a'&&a[r]%2==0)r--;
                   ^
/in/foo.cc:14:6: warning: array subscript has type 'char' [-Wchar-subscripts]
   a[r]--;
      ^
/in/foo.cc:15:6: warning: array subscript has type 'char' [-Wchar-subscripts]
   a[l]++;//把a[r]变为a[l] 为使字典序最小 
      ^
/in/foo.cc:19:9: warning: array subscript has type 'char' [-Wchar-subscripts]
   if(a[i]%2) 
         ^
/in/foo.cc:22:7: warning: array subscript has type 'char' [-Wchar-subscripts]
    a[i]--;
       ^
/in/foo.cc:24:6: warning: array subscript has type 'char' [-Wchar-subscripts]
   a[i]/=2;//先输出左边回文 
      ^
/in/foo.cc:25:21: warning: array subscript has type 'char' [-Wchar-subscripts]
   for(int j=1;j<=a[i];j++) cout<<i;
                     ^
/in/foo.cc:29:21: warning: array subscript has type 'char' [-Wchar-subscripts]
   for(int j=1;j<=a[i];j++)cout<<i;
                     ^