/in/foo.cc: In function 'int cc()':
/in/foo.cc:9:10: warning: unused variable 'o' [-Wunused-variable]
  int d=0,o=0;
          ^
/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:48:8: error: 'num' was not declared in this scope
   else num[i]=999999;
        ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:72:7: warning: unused variable 'step' [-Wunused-variable]
   int step=1;
       ^~~~