foo.cc:7:1: error: ‘dfs’ does not name a type
    7 | dfs dfs(int sx,int sy,int fx,int fy)
      | ^~~
foo.cc: In function ‘int main()’:
foo.cc:39:9: error: ‘dfs’ was not declared in this scope
   39 |         dfs(sx,sy,fx,fy);
      |         ^~~