/in/foo.cc:3:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:6:9: warning: unused variable 'br' [-Wunused-variable]
 int r,c,br,bc,n;
         ^~
/in/foo.cc:6:12: warning: unused variable 'bc' [-Wunused-variable]
 int r,c,br,bc,n;
            ^~