/in/foo.cc: In function 'bool bfs()':
/in/foo.cc:2:20: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
 #define rep(i,a,b) for(int i=(a);i<=(b);i++)
                    ^
/in/foo.cc:29:2: note: in expansion of macro 'rep'
  rep(i,1,n) dis[i]=-1; dis[S]=0;
  ^~~
/in/foo.cc:29:24: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
  rep(i,1,n) dis[i]=-1; dis[S]=0;
                        ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:103:8: warning: unused variable 'f1' [-Wunused-variable]
   bool f1,f2;
        ^~
/in/foo.cc:103:11: warning: unused variable 'f2' [-Wunused-variable]
   bool f1,f2;
           ^~