/in/foo.cc: In function 'void addflow()':
/in/foo.cc:51:9: warning: unused variable 'cost' [-Wunused-variable]
  double cost=0;
         ^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:68:8: warning: unused variable 'x' [-Wunused-variable]
  int i,x,y,j;
        ^
/in/foo.cc:68:10: warning: unused variable 'y' [-Wunused-variable]
  int i,x,y,j;
          ^