/in/foo.cc: In function 'int main()':
/in/foo.cc:9:10: warning: unused variable 'j' [-Wunused-variable]
  int n,i,j,k,x1,x2,y1,y2,a,b;
          ^
/in/foo.cc:9:12: warning: unused variable 'k' [-Wunused-variable]
  int n,i,j,k,x1,x2,y1,y2,a,b;
            ^