/in/foo.cc: In function 'int min_cost_flow(int, int, int)':
/in/foo.cc:71:13: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
   int d=f,a,b;
             ^
/in/foo.cc:71:11: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]
   int d=f,a,b;
           ^