/in/foo.cc: In function 'void merge_sort(int, int)':
/in/foo.cc:17:9: error: 'm' was not declared in this scope
   int q=m;
         ^
/in/foo.cc:30:5: error: 'con' was not declared in this scope
     con+=m-p;
     ^~~
/in/foo.cc:36:3: error: expected ';' before '}' token
   }
   ^