/in/foo.cc: In function 'void dijkstra()':
/in/foo.cc:28:8: warning: unused variable 'aaa' [-Wunused-variable]
    int aaa=len[u][j];
        ^~~
/in/foo.cc:25:10: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
   mark[u]=1;
   ~~~~~~~^~