/in/foo.cc: In function 'int main()':
/in/foo.cc:30:24: warning: array subscript has type 'char' [-Wchar-subscripts]
                 if(sf[c]) pd=1;
                        ^
/in/foo.cc:31:31: warning: array subscript has type 'char' [-Wchar-subscripts]
                 sf[stc[++to]=c]=1;
                               ^
/in/foo.cc:44:29: warning: array subscript has type 'char' [-Wchar-subscripts]
                 sf[stc[to--]]=0;
                             ^