foo.cpp: In member function 'void Link_Cut_Tree::splay(int)':
foo.cpp:31:15: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
             if(!isroot(y))
               ^
foo.cpp: In function 'int main()':
foo.cpp:60:17: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
                 if(lct.same(1,n))ans=min(ans,e[i].a+lct.val[lct.query(1,n)]);continue;
                 ^~
foo.cpp:60:78: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
                 if(lct.same(1,n))ans=min(ans,e[i].a+lct.val[lct.query(1,n)]);continue;
                                                                              ^~~~~~~~
foo.cpp:54:31: warning: unused variable 'a' [-Wunused-variable]
         int u=e[i].u,v=e[i].v,a=e[i].a,b=e[i].b;
                               ^
foo.cpp:68:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
     if(ans==inf)ans=-1;printf("%d\n",ans);
     ^~
foo.cpp:68:24: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
     if(ans==inf)ans=-1;printf("%d\n",ans);
                        ^~~~~~