/in/foo.cc: In function 'char fast_io::read()':
/in/foo.cc:10:28: warning: operation on 's' may be undefined [-Wsequence-point]
         return s==t?(((t=(s=buf)+fread(buf,1,IN_LEN,stdin))== s)?-1:*s++) : *s++;
                          ~~^~~~~
/in/foo.cc: In function 'void dfs1(int, int, int)':
/in/foo.cc:60:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0;i<edge[nown].size();i++){
                   ~^~~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void dfs2(int, int)':
/in/foo.cc:74:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0;i<edge[nown].size();i++){
                   ~^~~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void solve()':
/in/foo.cc:118:38: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
         dis = dep[a] + dep[b] + dep[c] - dep[a1] - dep[b1] - dep[c1];
                                 ~~~~~^
/in/foo.cc:118:29: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
         dis = dep[a] + dep[b] + dep[c] - dep[a1] - dep[b1] - dep[c1];
                        ~~~~~^
/in/foo.cc:118:20: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]
         dis = dep[a] + dep[b] + dep[c] - dep[a1] - dep[b1] - dep[c1];
               ~~~~~^
/in/foo.cc:33:38: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
             if (x < 0) print('-'), x = -x;
                                    ~~^~~~
/in/foo.cc:105:24: note: 'ans' was declared here
     int a,b,c,a1,b1,c1,ans,dis;
                        ^~~
/in/foo.cc: In function 'void init()':
/in/foo.cc:94:11: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int a,b;
           ^