View Compilation Error

0_0_25625067_23979.cpp: In function 'int main()':
0_0_25625067_23979.cpp:110:26: error: 'i' was not declared in this scope
   rt[1]=buildtree(1,sz(V[i]));
                          ^
0_0_25625067_23979.cpp:14:20: note: in definition of macro 'sz'
 #define sz(a) (int)a.size()
                    ^