/in/foo.cc: In function 'void spfa()':
/in/foo.cc:42:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for (i=1;i<=n;i++) dis[i]=1<<30;dis[start]=0;
     ^~~
/in/foo.cc:42:37: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
     for (i=1;i<=n;i++) dis[i]=1<<30;dis[start]=0;
                                     ^~~
/in/foo.cc: At global scope:
/in/foo.cc:52:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^