/in/foo.cc:7:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:10:10: warning: unused variable 'br' [-Wunused-variable]
  int r,c,br,bc,n;
          ^~
/in/foo.cc:10:13: warning: unused variable 'bc' [-Wunused-variable]
  int r,c,br,bc,n;
             ^~